Chapter 2. Pituitary and Adrenal Disorders of Pregnancy


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Chapter 2. Pituitary and Adrenal Disorders of Pregnancy

  1. 1. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy Pituitary and adrenal disorders provide challenges for diagnosis and treatment dur- ing pregnancy. PITUITARY DISORDERS IN PREGNANCY Anterior Pituitary Gland The pituitary enlarges throughout pregnancy, approximately 136% overall,1 and may become hyperintense on scan.2 This enlargement is due primarily to estrogen-stimulated hypertrophy and hyperplasia of the lactotrophs.3 Gonadotrophs decline in number, and corticotrophs and thyrotrophs remain constant.4 Somatotrophs are generally suppressed, and may function as lactotrophs.5 The peak pituitary size is seen in the first 3 days postpartum, when the gland height may reach 12 mm on MRI.1,6,7 The gland involutes rapidly following delivery regardless of breast feeding status, and is of normal size by 6 months postpartum.6,7 Prolactin (PRL) is secreted by the pituitary, hypothalamus, lymphocytes, uterus, pla- centa, and lactating mammary gland.8 In combination with other hormones, PRL me- diates mammogenesis, lactogenesis, galactopoiesis (maintenance of milk secretion), and plays a role in the regulation of humoral and cellular immune responses. Pla- cental estrogens stimulate lactotrophic PRL synthesis in the first trimester,9,10 while progesterone also stimulates prolactin secretion.11,12 Prolactin levels progressively increase approximately 10-fold throughout gestation,13 then decline postpartum in non-lactating women. Despite increased PRL levels, the normal lactotroph contin- ues to respond to TRH and anti-dopaminergic stimulation. Postpartum, the circadian rhythm of PRL release is enhanced by the effects of suckling. The placental growth hormone (GH) variant differs from pituitary GH by 13 amino acids and is synthesized by the syncytiotrophoblastic epithelium of the placenta. The regulation of placental GH secretion remains unknown, but this variant increases throughout gestation to levels of 10-20 ng/ml.14,15 This variant has similar carbo- hydrate, lipid,16 and somatogenic properties as pituitary GH, with less lactogenic activity.17 With this increase in overall GH activity, insulin-like growth factor 1 (IGF- 1) levels increase in the second half of pregnancy,18 contributing to the acromega- loid features of some pregnant women. Through negative feedback, pituitary GH levels consequently decline in the second half of gestation and the first week post- partum,14,15 with blunted response to hypoglycemic stimulation testing (not recom- mended in pregnancy), but normal response to GHRH.19 Patients with acromegaly have autonomous pituitary GH secretion, and both forms of GH persist in the blood throughout pregnancy.20 There is a transient fall in TSH in the first trimester during the 2nd and 3rd months. This is postulated to be secondary to human chorionic gonadotropin (hCG) stim- ulation of the thyroid due to the structural homology between the TSH and hCG molecules and their receptors.21 The role of hCG in increasing thyroid stimulating activity was first postulated with the thyrotoxicosis noted in molar pregnancies and trophoblastic disease,22 with cure after surgical excision of the mole or neoplasm. A negative correlation was later demonstrated between hCG and TSH in women undergoing elective abortion.23 Sequential TSH determinations between 8 and 14 weeks gestation revealed that the nadir in TSH coincides with the peak in hCG,24 with an inverse correlation found in individual samples such that TSH levels fall in a proportional and mirror response to the rise in <61538>hCG.(Figure 1)25 There is also a linear relationship between hCG and free T4 concentrations early in gesta- tion.24 In the majority of patients, this effect is transient and not clinically significant, as the peak of hCG is brief. However, sequential evaluations of TSH in a large co- hort of pregnant women revealed that 18% demonstrated transient subnormal TSH 1
  2. 2. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy in the 1st trimester, with 5% still subnormal in the 2nd trimester, with significantly higher levels of hCG found in these women than in those who maintained a nor- mal TSH.26 Furthermore, in hyperplacentosis27 and in twin pregnancies where the hCG peak is generally higher and of longer duration, there is more frequent and greater lowering of TSH than in singleton pregnancies.28 In the second half of ges- tation, TSH levels return to normal prepregnant levels. In iodine deficient regions, TSH increases near term but remains within the normal range.24 TSH demonstrates an increased response to TRH during gestation. The increase in estrogens produced by the fetal-placental unit stimulates hepatic production of thyroxine-binding glob- ulin and increases the sialylation of the TBG, thereby prolonging its half-life.29,30 This increase in TBG results in higher levels of total T4 and T3, starting at 4-6 weeks gestation.30 Free T4 levels may increase transiently in the 1st trimester as a result of the hCG peak. However, both free T4 and free T3 generally remain within the nor- mal range throughout gestation,24,29,30 though they may be 10-15% lower at term in iodine-sufficient women. Placental deiodination increases maternal T4 turnover. Figure 1. Maternal concentrations of serum TSH and hCG as a function of gesta- tional age. The decrease in serum TSH at approximately 10 week’s gestation may be due to thyrotropic effects of hCG. (From Glinoer D, de Nayer P, Bourdoux P, et al. Regulation of maternal thyroid during pregnancy. J Clin Endocrinol Metab 1990; 71:276.) Synthesis of hCG by syncytiotrophoblasts is itself partially stimulated by placental cytotrophoblast produced gonadotropin releasing hormone (GnRH). In response to placental sex steroid production, both hypothalamic GnRH and pituitary gonadotropin (FSH/LH) levels decline in the first trimester of pregnancy, with a blunted gonadotropin response to GnRH.31 FSH levels are initially suppressed postpartum, and return to normal by 3 weeks postpartum. LH levels tend to normalize more gradually. Corticotropin-releasing hormone (CRH) levels, synthesized primarily by the placental cytotrophoblasts and the decidua, rise several hundred fold by term.32,33 It stimulates both syncytotrophoblastic placental and pituitary adrenocorticotropic hormone (ACTH) production.34 ACTH levels consequently increase throughout 2
  3. 3. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy gestation, with a further increase in labor.35 The proportion of ACTH of pituitary vs. placental origin is unknown, however placental ACTH is not suppressible by dexamethasone administration. Cortisol levels progressively increase throughout gestation with a surge during labor.35 Cortisol binding globulin levels rise secondary to estrogen-stimulated production, leading to an increase in total cortisol of 2-3 fold by term.36 The “free” cortisol also rises 3-fold, with a 2-3 fold elevation in urinary free cortisol.35,36 Pituitary adenomas constitute 6.1% of primary intracranial (malignant and nonmalignant) neoplasms in women, with an age-adjusted incidence rate of 0.93 cases/100,000 person-years.37 The stimulatory effect of pregnancy on pituitary lactotrophs will impact a patient with a prolactinoma who becomes pregnant. Prolactinomas Hyperprolactinemia causes one third of all female infertility.38,39 It inhibits pulsatile gonadotropin secretion and the positive feedback of estrogen on gonadotropin secre- tion.39 Hyperprolactinemia has multiple potential etiologies. In patients with pro- lactinomas, treatment choices are defined by the clinical presentation and the thera- peutic goal. Surgical therapy is initially curative in approximately 70-80% of patients with mi- croadenomas and rarely causes hypopituitarism. The curative rate is much lower (30%) in patients with macroadenomas, and the risk of hypopituitarism and subse- quent infertility increases dramatically.39 For both microadenomas and macroade- nomas there is a recurrence rate of about 20%, therby lowering these long-term cure rates.39 Dopamine agonists are the primary therapy for the majority of patients with prolacti- noma. Bromocriptine, pergolide (approved for the treatment of Parkinson’s but not prolactinoma), and quinagolide (not approved in the United States) restore ovulatory menses in 70-80% of patients. Approximately 50-75% of patients with macroadeno- mas experience a > 50% reduction in size.39,40 Cabergoline is dosed once to twice weekly and is more effective and better tolerated than bromocriptine therapy with restoration of ovulatory menses in >90% of women,41 and >90% reduction in tumor size.39,42-45 To establish the intermenstrual interval prior to a pregnancy, mechan- ical contraception should be used for 2-3 cycles. This allows early recognition of a pregnancy so that the drugs are given for only 3-4 weeks of gestation. The long half- life of cabergoline causes fetal exposure for a further 1 or more weeks after cessation of therapy. Bromocryptine and cabergoline are approved for use in pregnancy, but not pergolide or quinagolide, and caution is certainly advised. The hormonal milieu of pregnancy may cause significant tumor enlargement in women with prolactin-secreting macroadenomas.(Figure 2) A review of published reports of pregnant patients with microadenomas previously treated with bromocriptine showed that only 12 of 457 (2.6%) pregnancies in women with microadenomas were complicated by symptoms of tumor enlargement (headaches and/or visual disturbances) (Table 1). Surgical intervention was not required in a single case but medical therapy with bromocriptine was instituted in 5 individuals. For patients with macroadenomas, 45 of 142 pregnancies (31%) were complicated by symptoms of tumor enlargement. Surgical intervention was undertaken in twelve of these cases and bromocriptine in 17. In addition, 140 women with macroadenomas were identified who had undergone surgery or radiation prior to pregnancy and their risk of tumor enlargement was 2.5%.46 Reinstitution of bromocriptine or cabergoline therapy generally is successful in reducing tumor size, though transsphenoidal surgery may be required.47,48 3
  4. 4. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy Figure 2. MRI scans with coronal (A,C) and sagittal (B,D) views demonstrating a prolactin-secreting macroadenoma before pregnancy (A,B) that progressively en- larged during pregnancy. The third trimester is shown here (C,D). The patient had been complaining of increasing headaches. Table 1. Effect of pregnancy on prolactinomas Total No. Patients Symptomatic % Symptomatic Enlargement Enlargment Microadenomas 457 12 2.6 Macroadenomas 142 45 31 Macroadenomas- 140 7 5 prior surgery or radiation Bromocriptine crosses the placenta,49 and continuous administration throughout gestation is not recommended. Experience with its use during the first few weeks of gestation has not been associated with increased risk for adverse events such as spontaneous abortion, ectopic pregnancies, multiple gestation, or congenital anomalies.(Table 2)47,50 Long-term studies of children exposed during the early first trimester have been limited to 64 children ranging in age from 6 months to 9 years, with no ill effects seen.51 In more than 100 pregnancies in which bromocriptine was used throughout gestation, the only neonatal abnormalities noted were a case of undescended testicle and one case of talipes deformity, which is in the expected range.47,50 4
  5. 5. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy Table 2. Effect of Bromocriptine on Pregnancies Bromocriptine Normal Population n % % Pregnancies 6,239 100.0 100.0 - spontaneous 620 9.9 10 - 15 abortion - terminations 75 1.2 - ectopic 31 0.5 0.5 - 1.0 - hydatidiform 11 0.2 0.05 - 0.7 moles Deliveries (known 4,139 100.0 100.0 duration) - at term (> 38 3,620 87.5 85 weeks) - preterm (< 38 519 12.5 15 weeks) Deliveries (known 5,120 100.0 100.0 outcome) - single births 5,031 9.3 8.7 - multiple births 89 1.7 1.3 Babies (known 5,213 100.0 100.0 details) - normal 5,030 96.5 95.0 - with 93 1.8 3-4 malformations - with perinatal 90 1.7 >2 disorders *Data from Krupp P, Monka C, Richter K. Program of the Second World Congress of Gynecology and Obstetrics. Rio de Janeiro, 1988, p. 9. There are few data on pergolide safety in pregnancy. It is known to cross the placenta in mice, with no teratogenicity noted in doses of 60 mg/kg/day.52 In one patient treated with pergolide in early gestation for Parkinson’s disease, no teratogenic or developmental abnormalities were noted in the offspring.53 However, the authors mentioned 2 major and 3 minor congenital anomalies in 38 pregnancies exposed to pergolide in premarketing studies, with causality not established.53 The manufac- turer, Eli Lilly & Co., has limited data on pregnancies in which the fetus was exposed to pergolide. There was no information on 43.4% of pregnancies, 7.2% of pregnancies ended in spontaneous abortion, 7.2% had minor malformations, 14.3% underwent in- tentional abortions, and 28.6% delivered healthy infants.54 Alternatives to pergolide therapy should be found for women desiring pregnancy. Quinagolide should not be used when pregnancy is desired. A review of 176 preg- nancies in which quinagolide was maintained for a median of 37 days, reported 13.6% spontaneous abortions, 0.6% ectopic pregnancies, 0.6% stillbirths at 31 weeks, and 5.1% malformations: spina bifida, trisomy 13, Down syndrome, talipes, cleft lip, arrhinencephaly, and Zellweger syndrome.55 Cabergoline has been utilized in the first trimester in more than 350 human pregnan- cies. To date, there is no evidence for increased risk of spontaneous abortion, congen- ital anomalies, multiple gestation, or premature delivery.56-61 Normal physical and 5
  6. 6. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy mental development was seen in 107 infants followed 1-72 months.56 There is little specific data regarding the use of transsphenoidal surgery during preg- nancy. It is presumed that the risks would be similar to other forms of surgery, except for the increased risk of hypopituitarism. For patients with intrasellar tumors, bromocriptine or cabergoline therapy is pre- ferred as it is safe for the fetus if it is discontinued early in gestation. These tumors demonstrate a small risk for tumor enlargement. Patients should be followed on a trimester basis for symptomatic enlargement, such as headaches or visual problems. Visual field testing should be performed if clinically indicated. Therapeutic options for tumors extending outside the sella include prepregnancy surgical debulking, intensive monitoring without dopamine agonist therapy, or con- tinuous bromocriptine therapy throughout gestation. The latter is not likely to harm the fetus but the number of cases followed in this way is small. Patients require monthly assessments and visual field examinations every trimester. Prolactin lev- els provide little benefit in the clinical assessment, as they may not rise with tumor enlargement.62 With evidence of tumoral enlargement, bromocriptine should be im- mediately reinstituted and the dose rapidly titrated as tolerated. Switching to caber- goline therapy, transsphenoidal surgery, or delivery if gestation length is adequate, should be considered if the response to bromocriptine therapy is inadequate.47 Breastfeeding stimulates prolactin secretion in normal women in the first few weeks or months postpartum.39 However, there is no evidence that suckling stimulates pro- lactinoma growth. Therefore, we do not discourage breastfeeding in women with prolactinomas. However, dopamine agonists must be withheld until the period of breastfeeding is over. Anovulation secondary to hyperprolactinemia in untreated women is associated with hypoestrogenemia and a potential for osteoporosis.39 Although the estrogen in oral contraceptives stimulates lactotrophs and mild increases in prolactin levels in normal women, it does not usually cause growth of microadenomas or precipitate neoplastic development in women with idiopathic hyperprolactinemia.63 Prolactin levels should be evaluated periodically to find the rare estrogen-sensitive tumor. If prolactin levels are found to increase substantially, the estrogen should be stopped to forestall tumor growth. For patients with macroadenomas, dopamine agonists are preferred because of their efficacy in reducing tumor size. Acromegaly Infertilily is common in women with acromegaly, as approximately 75% of acrome- galic women of child-bearing years have menstrual irregularity.64 The ovarian dys- function is often the result of the hyperprolactinemia found in 30-40% of cases65 and to possible mass effects of the tumor. An additional factor is the coexisting polycystic ovary disease seen in a number of patients.66 Many patients require bromocriptine to ovulate and conceive, and normalization of the hyperprolactinemia frequently re- stores menstruation. GH and IGF-1 also regulate ovarian function, as GH increases ovarian responsiveness to gonadotropins67 either directly or through IGF-1 produc- tion in the ovarian follicle.68 Pituitary growth hormone secretion is autonomous in acromegaly, so both pituitary and placental GH variants persist throughout pregnancy.69 Diagnosing acromegaly during gestation may be difficult as conventional assays are unable to distinguish between the 2 forms of GH. This distinction requires special assays with antibod- ies which recognize specific epitopes on the pituitary and placental GH variants.14 However, pituitary growth hormone secretion in acromegaly demonstrates a pul- satility of 13-19 pulses per 24 hours,70 vs. the tonic secretion seen with the placental variant.15 In addition, paradoxical GH release after TRH occurs with pituitary GH excess,65 and is not seen with the placental variant.69 Postpartum, the placental vari- ant disappears from the circulation within 24 hours.14 IGF-1 levels are not useful in 6
  7. 7. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy the diagnosis of acromegaly in pregnancy, as they elevate in the second half of both normal and acromegalic pregnancies.71 Pregnancy was thought to exacerbate the underlying condition in 4 of 24 (17%) preg- nant patients with acromegaly who have been described in the literature.72 Tumor enlargement during pregnancy has been described in 2 patients with acromegaly, leading to a visual field defect in one.73,74 Symptomatic tumor enlargement should be monitored monthly, with visual field testing every trimester. Glucose tolerance, hypertension, and cardiac derangements also require monitoring.65 Glucose intol- erance occurs in 50% of patients with acromegaly, with overt diabetes mellitus in 10-20%.65 The risk for gestational diabetes mellitus is consequently increased by the insulin resistance of acromegaly. Sodium retention leads to hypertension in 25-35% of patients, with potential for exacerbation in pregnancy. Cardiac disease is present in one third of patients with acromegaly, with underlying cardiomyopathy and in- creased risk for coronary artery disease, which may also be exacerbated during preg- nancy.65,75 GH does not cross the placenta, and maternal acromegaly has little direct impact on the fetus. Fetal somatic growth is largely GH-independent, and macrosomia in such pregnancies is likely secondary to maternal glucose intolerance. Bromocriptine and cabergoline therapy may provide limited benefit in treating individuals with acromegaly, with no reduction in tumor size and rare normalization of GH levels. Their use in pregnancy has been described above. Neither dopamine agonist should be continued throughout pregnancy in most patients. Somatostatin analogs can cross the placenta. Ten cases have been described of women with acromegaly treated with octreotide during pregnancy,75-77 two cases with acromegaly treated with lanreotide,78,79 one with a TSH-secreting tumor treated with octreotide during pregnancy,80 and one with nesidioblastosis treated with octreotide during pregnancy.81 In most cases the somatostatin analog was stopped before the end of the first trimester, but in two cases octreotide was given throughout the pregnancy.75,81 No malformations were noted. However, octreotide crosses the placenta and somatostatin receptors are widespread in many tissues including the brain; therefore, there certainly is the potential for somatostatin analogs to affect developing fetal tissues.82 Octreotide and lanreotide are not approved for use in pregnancy. Interruption of medical therapy for 9-12 months should have limited impact on the long-term outcome of patients with acromegaly. For enlarging tumors, reintroduction of somatostatin analogs vs. surgery should be considered. Other Pituitary Adenomas The ACTH-secreting neoplasms will be described in the adrenal disorders section. There are few data regarding gonadotropin-secreting or TSH-secreting pituitary ade- nomas in pregnancy. Treatment of three cases of TSH-secreting adenomas has been reported.80,83-85 Octreotide was used in two cases. In one octretide was continued to control tumor size, and the second it was reinstituted to control tumor size. The hyperthyroidism may be controlled with standard antithyroid drug therapy.84 Clinically non-functioning adenomas are primarily gonadotroph adenomas.86 Although unlikely to enlarge under the influence of estrogen stimulation in pregnancy, the lactotroph hyperplasia which occurs can cause chiasmal compression or headaches in a patient with a preexisting clinically non-functioning adenoma. Two cases have been reported of tumor enlargement in pregnancy with resulting visual field defect.73,87,88 In one case, the patient responded to bromocriptine therapy which reduced the lactotroph hyperplasia and had little or no direct effect on the neoplasm.88 Two patients with gonadotroph adenomas secreting intact follicle-stimulating hormone developed ovarian hyperstimulation syndrome.89,90 Pregnancy occurred in both, after bromocriptine therapy in one89 and surgery in the second.90 7
  8. 8. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy Hypopituitarism Hypopituitarism, secondary to neoplastic, vascular, traumatic, or infiltrative disor- ders, is commonly associated with gonadotropin deficiency and infertility. Fertility is possible with the assistance of the reproductive endocrinologist, using human chori- onic gonadotropin and follicle-stimulating hormone, pulsatile GnRH, and in vitro fertilization. During gestation, adrenal and thyroid hormones should be replaced as needed. The average increase in levothyroxine required during gestation is 0.05 mg/day. Adrenal hormone replacement in pregnancy is discussed below. Hypopituitarism may also present during pregnancy or postpartum, secondary to adenoma expansion, lymphocytic hypophysitis, and pituitary infarction. Recognition may be difficult because fatigue, nausea, and vomiting are frequent accompaniments of normal pregnancies. Dynamic testing during pregnancy is also difficult to interpret in light of the physiologic changes during normal pregnancy. Inadequately treated hypopituitarism may lead to poor pregnancy outcome, including spontaneous abor- tion, intrauterine fetal demise, maternal hypotension, hypoglycemia, and even ma- ternal death. Sheehan’s Syndrome Sheehan’s syndrome consists of pituitary necrosis secondary to ischemia occurring within hours of delivery.91,92 It is usually secondary to hypotension and shock from an obstetric hemorrhage. Pituitary enlargement during pregnancy apparently pre- disposes to the risk for ischemia with occlusive spasm of the arteries to the anterior pituitary and stalk.91,92 The degree of ischemia and necrosis dictates the subsequent patient course. It rarely occurs with current obstetric practice.93 Acute necrosis is suspected in the setting of an obstetric hemorrhage where hypotension and tachycardia persist following adequate replacement of blood products.(Table 1) In addition, the woman fails to lactate and may have hypoglycemia.91,92,94 Investigation should include levels of ACTH, cortisol, prolactin, and free thyroxine. The ACTH stimulation test would be normal, as the adrenal cortex would not be atrophied. Thyroxine levels may prove normal initially, as the hormone has a half-life of seven days. Prolactin levels are usually low, although they are generally 5-10 fold elevated in the puerperium,. Treatment with saline and stress doses of corticosteroids should be instituted immediately after drawing the blood tests. Additional pituitary testing with subsequent therapy should be delayed until recovery. Diabetes insipidus may also occur secondary to vascular occlusion with atrophy and scarring of the neurohypophysis.95 When milder forms of infarction occur, the diagnosis of Sheehan’s syndrome may be delayed for months or years.95 These women generally have a history of amen- orrhea, decreased libido, failure to lactate, breast atrophy, loss of pubic and axillary hair, fatigue, and symptoms of secondary adrenal insufficiency with nausea, vomit- ing, diarrhea, and abdominal pain.(Table 3)95 Some women experience only partial hypopituitarism, and may have normal menses and fertility.94 Although the women may have episodes of transient polydipsia and polyuria, many demonstrate impaired urinary concentrating ability and deficient vasopressin secretion.96 CT or MRI scans generally reveal partial or completely empty sellae.97 Table 3. Symptoms and Signs of Sheehan Syndrome Acute Form Chronic Form 8
  9. 9. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy Acute Form Chronic Form Hypotension Light-headedness Tachycardia Fatigue Failure to lactate Failure to lactate Hypoglycemia Persistent amenorrhea Failure to regrow shaved pubic hair Decreased body hair Extreme fatigue Dry skin Nausea and vomiting Loss of libido Nausea and vomiting Cold intolerance (From Molitch ME. Pituitary, thyroid, adrenal and parathyroid disorders. In: Barron WM, Lindheimer MD, eds. Medical disorders during pregnancy. Chicago: Mosby-Year Book, 1991.) Lymphocytic Hypophysitis Lymphocytic hypophysitis is thought to be autoimmune in nature, and is manifested by a massive infiltration and destruction of the parenchyma of the pituitary and in- fundibulum by lymphocytes and plasma cells.98 It generally occurs during preg- nancy or the postpartum period, perhaps related to the <61485>enolase autoantigen shared by both the pituitary and placenta.99 It is associated with symptoms of hy- popituitarism or an enlarging mass lesion with headaches and visual field defects, and is suspected based on its timing and lack of association with an obstetric hemor- rhage or prior history of menstrual difficulties or infertility. It is generally associated with mild hyperprolactinemia (<150 ng/ml) and diabetes insipidus. Differentiation from a pituitary neoplasm cannot be made based on CT or MRI scans which reveal a sellar mass with possible extrasellar extension, but only on biopsy results.100,101 Serum antibodies to human pituitary membrane antigens are specific, but not sensi- tive, for diagnosis.102 Treatment is generally conservative and involves identification and correction of any pituitary deficits, particularly of ACTH secretion, which is par- ticularly common in this condition.103 There are no data to indicate that high dose corticosteroids are of benefit in treating the destructive process. Surgery to debulk but not remove the gland is indicated in the presence of uncontrolled headaches, visual field defects, and progressive enlargement on scan. Spontaneous regression and re- sumption of partial or normal pituitary function may occur, although most patients progress to chronic panhypopituitarism.103-105 Other autoimmune disorders may also be associated. Posterior Pituitary Hyperventilation in pregnancy leads to hypercapnea, renal bicarbonate wasting, and associated renal sodium loss. The osmostat, the setpoint for plasma osmolality at which arginine vasopressin (AVP) is secreted, is reduced approximately 5-10 mOsm/kg in pregnancy, dropping from 285 to 275 mOsm/kg. As a result, pregnant women experience thirst and release AVP at lower levels of plasma osmolality than do nonpregnant women.106 This reset osmostat and altered thirst threshold is possibly due to high levels of human chorionic gonadotropin (hCG).106 The 9
  10. 10. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy placenta produces an amino-terminal peptidase, vasopressinase, an enzyme that rapidly inactivates AVP and oxytocin. Vasopressinase levels increase 1000-fold between the 4th and 38th weeks of gestation.107 AVP consequently has a four- to sixfold increased metabolic clearance rate during gestation.108,109 The lower osmostat and increased clearance of AVP by vasopressinase in pregnancy alter the nomograms of plasma osmolality and AVP used in the nonpregnant pa- tient. Serum sodium levels may also be lower than those normally expected in pa- tients with diabetes insipidus.109 Standard water deprivation tests which require 5% weight loss should be avoided during pregnancy as they may cause uterine irritabil- ity and alter placental perfusion. Instead, dDAVP is used to assess urinary concen- trating ability over 11 hours, with a value greater than 700 mosm/kg considered nor- mal.110 Urinary concentrating ability in the pregnant patient should be determined in the seated position, as the lateral recumbent position inhibits maximal urinary concentration.106,109 Delivery of the placenta generally results in a return to normal AVP metabolism in 2 to 3 weeks. Plasma oxytocin levels increase progressively during pregnancy, with a dramatic in- crease at term.111,112 Oxytocin levels rise further during labor and peak in the sec- ond stage. Uterine sensitivity to oxytocin increases with a rise in oxytocin receptors in the myometrium. Hypophysectomy does not alter onset of labor, indicating that oxytocin provides only a facilitatory role.113 Pulsatile release of oxytocin does not correlate with uterine contractions. Oxytocin levels rise rapidly during suckling.114 Diabetes Insipidus Three types of diabetes insipidus may occur in pregnancy; central, nephrogenic, or transient vasopressin-resistant. Each is manifest with polydipsia, polyuria, and de- hydration. Central diabetes insipidus may occur spontaneously in pregnancy with an enlarging pituitary adenoma, with lymphocytic hypophysitis, or with the development of other conditions such as histiocytosis X. Diabetes insipidus usually worsens during gestation,109 likely due to the increased clearance of AVP by the vasopressinase. Patients with asymptomatic DI may develop symptoms during pregnancy with the lower osmostat for vasopressin release, elevation in vasopressinase levels, and increased AVP clearance.115-117 Patients with mild disease usually treated with chlorpropamide should discontinue this agent, as it readily crosses the placenta and causes hypoglycemia in the fetus. The AVP analog desmopressin (dDAVP) is resistant to vasopressinase, and provides satisfactory treatment during gestation, although a higher dose may be required.109 During monitoring of the clinical response, clinicians should remember that normal basal plasma osmolality and sodium concentration are 5 mEq/L lower during pregnancy.118 No adverse events have been described in the offspring of pregnancies in which dDAVP was used throughout gestation.119,120 DDAVP transfers minimally into breast milk109 and is poorly absorbed from the gastrointestinal tract, so its use will not adversely affect an infant’s water metabolism. Transient AVP-resistant forms of DI secondary to placental production of vasopressi- nase may occur spontaneously in one pregnancy, but not in a subsequent one.118 Some of these patients may respond to dDAVP therapy. The symptoms resolve within several weeks of delivery.109,118,121 Acute fatty liver of pregnancy and other disturbances of hepatic function such as hepatitis may be associated with late onset transient DI of pregnancy in some patients.122,123 It is presumed the hepatic dysfunction is associated with reduced degradation of vasopressinase, further increasing vasopressinase levels and the clearance of AVP. The polyuria may develop either prior to delivery or postpartum. Complete resolution of the hepatic abnormalities and DI occurs by the 4th week postpartum. 10
  11. 11. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy DI that develops postpartum may be a result of Sheehan’s syndrome, particularly in the setting of an obstetric hemorrhage.(see above) Transient DI of unknown etiology has been described postpartum, lasting only days to weeks.124 Congenital nephrogenic DI is a rare X-linked disorder caused by a mutation in the va- sopressin V2 receptor gene, and predominantly affects males. Female carriers of this disease may have significant polyuria during pregnancy. Treatment is with thiazide diuretics,109 which should be used with caution in pregnant women. In patients with idiopathic DI, oxytocin levels are normal and labor may begin spon- taneously and proceed normally.125 Patients with DI secondary to trauma, infiltra- tive disease, or a neoplasm may have adversely affected oxytocinergic pathways, resulting in poor progression of labor and uterine atony. ADRENAL DISORDERS IN PREGNANCY Pregnancy modifies adrenal steroid metabolism substantially. Unlike the hypothalamic-pituitary-adrenal axis, glucocorticoid levels provide a postitive feedback on the placental corticosteroid axis. Placental CRH rises several hundred-fold during pregnancy, is extensively protein bound until term, and modulates both maternal and fetal pituitary-adrenal axes and may regulate parturition.126 Both maternal and placental ACTH levels rise dramatically after 16-20 weeks gestation,(Figure 3)127 with a final surge in ACTH and plasma cortisol during labor. Despite the increase in the placental hormones, the normal maternal circadian rhythm of ACTH secretion persists throughout pregnancy. 11
  12. 12. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy Figure 3. Plasma concentrations of adrenocorticotropic hormone (ACTH) and corti- sol during normal pregnancy. Blood samples were obtained from five normal preg- nant women weekly at 8:00 to 9:00 AM and from three women during labor and on the second postpartum day. In addition, umbilical cord plasma was obtained from the newborn infants of three of these subjects. The mean plasma concentrations for ACTH are denoted by the solid circles, whereas plasma cortisol levels are denoted by open circles. The vertical bars correspond to the magnitude of the standard er- ror of the mean. (From Carr BR, Parker Jr CT, Madden JD, et al. Maternal plasma adrenocorticotropin and cortisol relationships throughout human pregnancy. Am J Obstet Gynecol 1981;139:416.) The fetoplacental unit has a marked capacity for steroidogenesis. At the same time, maternal cortisol levels increase 2- to 3-fold throughout pregnancy,128,129 with an in- crease in the size of the maternal zona fasciculata.130 There is an estrogen-stimulated increase in circulating cortisol binding globulin levels, resulting in an increase in to- tal cortisol levels and a decreased rate of cortisol clearance.131 With displacement of cortisol from CBG by progesterone, free cortisol levels also increase.128 Urine free cortisol levels rise 2-3 fold during gestation. Numerous changes occur in the renin-angiotensin-aldosterone system as well. Plasma renin activity increases 3- to 7-fold and plateaus at 20 weeks gestational age, despite the increase in plasma volume with pregnancy.132,133 Angiotensin II levels increase approximately 3-fold by term, although there is resistance to its pressor effects. Plasma mineralocorticoid levels increase 5- to 20-fold during gestation,129,133 but aldosterone secretion continues to respond normally to physiologic stimuli such as posture and varies inversely to changes in volume or 12
  13. 13. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy dietary salt.134,136 The increase in aldosterone correlates with the pregnancy increase in GFR and in progesterone,135 which competitively inhibits sodium retention by aldosterone at the distal renal tubules. Progesterone also demonstrates an anti-kaliuretic effect,136 with a report of amelioration of hypokalemia during pregnancy in a woman with primary aldosteronism.137 The relative hypercortisolism and hyperaldosteronism of normal pregnancy are not generally clinically apparent. Adrenal disorders occurring in pregnancy cause signif- icant maternal and fetal morbidity. Cushing’s Syndrome During Pregnancy Cushing’s syndrome is uncommon, with an incidence of 2 in 1,000,000. Just over 100 cases have been reported in pregnancy to date.138-156 Fertility is generally reduced by the altered gonadotropin secretion in pituitary disease, and increased adrenal androgen secretion in adrenal disease. Anovulation may be less prevalent with adrenal Cushing’s syndrome, as the proportion of adrenal and pituitary disease in pregnancy differs from that found in the nonpregnant woman. Approximately 40% of cases are secondary to a pituitary adenoma vs. an 80% rate expected in the nonpregnant woman. Of the remaining, 44% are adrenal adenomas, 11% adrenal carcinomas,138-144 and the remainer a mix of primary pigmented nodular adrenal disease, ACTH-independent hyperplasia, and ectopic ACTH secretion.140 Several cases of pregnancy-dependent Cushing’s syndrome have been described, with no interpartum adrenal steroid abnormalities noted.145,146,153 The placental CRH rise apparently caused a pregnancy-induced exacerbation and recognition of the hypercortisolism, with occasional improvement in the symptoms postpartum.139,140 Recurrent Cushing’s syndrome may occur in pregnancy with remission postpartum.141,154 It may be difficult to diagnose Cushing’s syndrome during pregnancy because the typical symptoms of central weight gain, fatigue, emotional lability, glucose intol- erance, hypertension, and edema are also common accompaniments of pregnancy. Pigmentation of striae and development of hirsutism or acne may suggest the hy- perandrogenemia of Cushing’s syndrome, and proximal myopathy may also help to distinguish Cushing’s syndrome from normal pregnancy symptoms. Pathologic fractures may occur.157 The laboratory evaluation is confounded by the normal preg- nancy rise in ACTH and cortisol levels. The hypercortisolism of pregnancy continues to exhibit a normal circadian rhythm, though with a higher nighttime nadir; loss of diurnal rhythm is characteristic of all forms of Cushing’s syndrome.147 Salivary cor- tisol measurements may assist in determining this lack of diurnal response, but nor- mal midnight levels have not been standardized for pregnancy.153,155,156,158 Uri- nary free cortisol levels greater than 3 times the upper limit of normal may be inter- preted as indicating Cushing’s syndrome in the second and third trimester. There are limited or no data using antibody-based assays or mass spectrometry. Normal preg- nancy is also associated with “inadequate” suppression of ACTH and cortisoldur- ing the overnight dexamethasone suppression test.141 ACTH levels may not reliably distinguish between pituitary and adrenal etiologies, as the levels may be normal or high in all forms of Cushing’s syndrome, likely from placental ACTH production or from the placental CRH-stimulated pituitary ACTH production.138-144,155,156,159 When plasma ACTH levels are suppressed, preferably as measured using a two-site immunometric assay, no further biochemical testing is needed. The high-dose dexamethasone suppression test (HDST) will cause > 80% suppression of serum cortisol in normal pregnancy. Patients with adrenal Cushing’s may be iden- tified with this test as they don’t suppress, but the HDST may misclassify those with Cushing’s disease, as three of seven cases failed to suppress in a small series.155,156 Petrosal sinus sampling with CRH stimulation (pregnancy category C) has been used with no ill effects using the direct jugular vein approach to minimize fetal irradi- ation.148,155 Clear central-to-peripheral ACTH gradients were found. Response to CRH stimulation testing is variable. Ross et al142 described the typical exaggerated ACTH response to CRH in one patient, while Mellor et al152 saw only a doubling of 13
  14. 14. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy cortisol levels in response to CRH in another patient. Lindsay et al155 found a more than threefold increase in ACTH but a less than twofold elevation in cortisol levels in 2 patients. Pituitary MRI, performed without gadolinium enhancement, is often non- diagnostic in patients with Cushing’ syndrome. Adrenal ultrasound may be used to characterize adrenal lesions in patients with borderline or low plasma ACTH or no suppression on the HDST. Maternal complications of Cushing’s syndrome include hypertension, preeclampsia, diabetes, myopathy, opportunistic infections, and fracture. Postoperative wound in- fection and dehiscence may occur following cesarean delivery. Premature labor oc- curs in more than 50% of cases.138-144,150-153,155,156 Fetal effects include intrauter- ine growth retardation, effects of prematurity, and 25% mortality from spontaneous abortion, stillbirth, and prematurity.138-144,150-153,155,156 The maternal hypercor- tisolemia may occasionally lead to fetal adrenal suppression,149 and the neonate should be tested for this and treated prophylactically until the results are known. Rates of fetal loss and premature labor decrease, though are still significant, in patients who are treated during pregnancy.138,141 In two published reviews, fetal loss rates of 30% and 38% were seen in 26 and 43 women for whom treatment was delayed, vs. 9% and 24% in 11 and 17 women who were treated during pregnancy.138,141 Similarly, premature labor rates were 48% and 72% in the 26 and 43 women for whom treatment was delayed, vs. 20% and 47% in the 11 and 17 women who were treated.138,141 Medical therapy is generally not effective,140,141,144 though it may be used pending definitive surgical therapy. Metyrapone has proved efficacious in a few patients, with side effects including hypertension and preeclampsia.160-162 Ketoconazole therapy in three patients was associated with intrauterine growth retardation, but no malformations or neonatal adrenal insufficiency.150,151,155 Aminoglutethamide may cause fetal masculinization and mitotane is teratogenic; both should be avoided. Adrenal surgery may be performed using a laparoscopic approach. The live birth rate is approximately 87% after unilateral or bilateral adrenalectomy.155,156 Because of the high rate of adrenal carcinoma, early surgery may improve the poor prognosis. Transsphenoidal surgery has also been used successfully.139,142,148,149,152,153,155,156 The risks of surgery to both mother and fetus are outweighed by the benefits of appropriately treating the Cushing’s syndrome. Adrenal Insufficiency The prevalence of primary adrenal insufficiency in pregnancy is unknown, with a series from Norway suggesting an incidence of 1 in 3000 births from 1976 to 1987.163 In developed countries, the most common etiology for primary adrenal insufficiency is autoimmune adrenalitis, which may be associated with autoimmune polyglan- dular syndrome. Primary adrenal insufficiency from infections (tuberculous or fun- gal), bilateral metastatic disease, hemorrhage or infarctions is uncommon. Secondary adrenal insufficiency, from pituitary neoplasms or glucocorticoid supression of the hypothalamic-pituitary-adrenal axis, is more common. Recognition of adrenal insufficiency may be difficult in the first trimester as many of the clinical features are found in normal pregnancies, including weakness, light- headedness, syncope, nausea, vomiting, hyponatremia, and increased pigmentation. Addisonian hyperpigmentation may be distinguished from chloasma of pregnancy by its presence on the mucous membranes, on extensor surfaces, and on non-exposed areas. Weight loss, hypoglycemia, salt craving, hyponatremia more severe than the normal 5 mmol/L decrease of pregnancy, or seizures, should prompt a clinical eval- uation. If unrecognized, adrenal crisis may ensue at times of stress, such as a urinary tract infection or labor.163 Fetal cortisol production may be protective, shielding the mother from severe adrenal insufficiency until postpartum.164 The fetoplacental unit largely controls its own steroid milieu, so maternal adrenal insufficiency generally causes no problems with fetal development. Maternal anti- 14
  15. 15. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy adrenal autoantibodies may cross the placenta, but usually not in sufficient quanti- ties to cause fetal or neonatal adrenal insufficiency.165 Although earlier studies ob- served intrauterine growth retardation in offspring of women with Addison’s dis- ease,166,167 this observation has not been supported in most subsequent case series. Severe maternal hyponatremia or metabolic acidosis may cause a poor fetal outcome, including death.168 Association with other autoimmune conditions such as anticar- diolipin antibodies may lead to additional risks such as miscarriage.169 Adrenal insufficiency is associated with laboratory findings of hyponatremia, hyper- kalemia, hypoglycemia, eosinophilia, and lymphocytosis. Hyperkalemia may be ab- sent, because of the pregnancy increase in the renin angiotensin system.168,170 Early morning plasma cortisol levels of < 3.0 mcg/dl (83 nmol/L) confirms adrenal insuf- ficiency,171 while a cortisol >19 mcg/dl (525 nmol/L) in the first or early second trimester excludes the diagnosis in a clinically stable patient.171,172 Plasma corti- sol levels may fall in the normal “nonpregnant” range due to the increase in CBG concentrations in the second and third trimesters, but will not be appropriately ele- vated for the stage of pregnancy. Appropriate pregnancy-specific cutoffs for diagno- sis with the standard cosyntropin (1-24 corticotropin) test using a 250 mcg dose have not been established. Plasma cortisol levels were 60% to 80% above nonpregnant re- sponses in normal pregnant women tested in the second and third trimesters in one series.173 McKenna et al171 examined the 1 mcg low dose cosyntropin test for di- agnosis of secondary adrenal insufficiency in women at 24-34 weeks gestational age, and found high sensitivity of diagnosis using a cutoff of 30 mcg/dl (828 nmol/L). Accuracy of dosing is more difficult with this than with the standard cosyntropin test. The cosyntropin test is less sensitive to detect early secondary or tertiary forms of adrenal insufficiency. Cortisol and ACTH responses to CRH are blunted in preg- nancy,174 making the CRH stimulation test unreliable for differentiating secondary and tertiary adrenal insufficiency in pregnancy. With primary adrenal insufficiency, ACTH levels will be elevated, and a level above 100 pg/ml (22 pmol/L) is consis- tent with the diagnosis.172 However, ACTH will not be low with secondary forms because of the placental production of this hormone, which is nevertheless insuffi- cient to maintain normal maternal adrenal function. ACTH values fluctuate widely, and a single value is insufficient for diagnosis. Adrenal antibodies may assist in con- firming idiopathic adrenal insufficiency, as approximately 90% of patients will have 21-hydroxylase antibodies and 30% will have antibodies to 17-hydroxylase and side- chain cleavage enzymes.175 Aldosterone to renin ratios are low with elevated plasma renin activity in patients with mineralocorticoid deficiency from adrenal atrophy.176 In the unstable patient, empiric glucocorticoid therapy (hydrocortisone 100 mg IV) should be administered pending the results of diagnostic testing. Thereafter, stress doses of 50-100 mg every 6-8 hours during the crisis mimics the maximal cortisol pro- duction rates of 200 to 300 mg/day.177 Despite the normal increase in plasma cortisol during pregnancy, baseline maternal replacement doses of corticosteroids usually are not different from those required in the non-pregnant state. Higher doses are needed at times of stress, such as during the course of “morning sickness” or during labor and delivery. Patients should be educated in the self-administration of intramuscular hydrocortisone. Hydrocortisone 50 mg IV is generally given in the second stage of labor.178 Mineralocorticoid replacement requirements usually do not change during gestation, though some clinicians have reduced doses of fludrocortisone in the third trimester in an attempt to treat Addisonian patients who develop edema, exacerba- tion of hypertension, and preeclampsia.163,179 Patients who have received glucocorticoids as antiinflammatory therapy are presumed to have adrenal axis suppression for at least one year.180 These patients should be treated with stress doses of glucocorticoids during labor and delivery. They are at risk for postoperative wound infection and dehiscence as are patients with endogenous Cushing’s, and their offspring are at risk for transient adrenal insufficiency. Although prednisone readily crosses the placenta,181 the maternal:fetal gradient is higher than with other available agents.182,183 Corticosteroid therapy during pregnancy is generally safe and suppression of neonatal adrenal function is uncommon.184 Glucocorticoid therapy during lactation 15
  16. 16. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy is also safe, as less than 0.5% of the dose is passed into breast milk.167,185 Congenital Adrenal Hyperplasia Congenital adrenal hyperplasia occurs in a family of monogenic inherited enzymatic defects of adrenal steroid biosynthesis, with manifestations secondary to an accumulation of precursors proximal to the enzymatic deficiency. The most common form of CAH in the population is 21-hydroxylase (CYP21 gene) deficiency, seen in more than 90% of the CAH cases in pregnancy.186-188 Classic, severe 21-hydroxylase deficiency is associated with ambiguous genitalia, an inadequate vaginal introitis, and progressive postnatal virilization including precocious adrenarche, advanced somatic development, central precocious puberty, menstrual irregularity, a reduced fertility rate, and possibly salt wasting.187,189,190 The spontaneous abortion rate is twice that in the normal population,191 and congenital anomalies are more frequent. Cephalopelvic disproportion from an android pelvis may occur, sometimes complicated by the previous reconstructive surgery.192,193 Conception requires adequate glucocorticoid therapy, which then continues at stable rates during gestation, except at labor and delivery. Nonclassic (late-onset) 21-hydroxylase deficiency patients present with pubertal and postpubertal hirsutism and menstrual irregularity, and may have improved fertility with glucocorticoid therapy.191 Fetal risk depends on the carrier status of the father. Unfortunately, ACTH stimulation testing to measure 17-OH progesterone demonstrates overlap between heterozygotes for CAH and the normal population.194 Ideally, CYP21 genotyping should be performed.188 Virilization is not seen in the female fetus with nonclassic 21-hydroxylase deficiency,195 but occurs in a fetus with classic 21-hydroxylase deficiency unless fetal adrenal androgen production is adequately suppressed. Dexamethasone most readily crosses the placenta as it is not bound to CBG and is not metabolized by placental 11 hydroxysteroid dehydrogenase. It is commonly used at doses of 20 µg/kg maternal body weight per day to a maximum of 1.5 mg daily in 3 divided doses beginning at recognition of pregnancy before the 9th week of gestation,187,189 though lower doses are recommended by some.196 Treatment by the 9th week of gestation is very effective in reducing the risk of virilization in the affected female fetus.189 Maternal plasma and/or urinary estriol levels reflect fetal adrenal synthesis and are monitored to assess efficacy. Maternal cortisol and DHEA-S levels will represent maternal adrenal suppression. There is little effect on maternal 17-OH progesterone with therapy. As only 25% of female fetuses are affected in a family with CAH, it is important to discontinue therapy as soon as possible in the male fetus and unaffected female fetus. Chorionic villus sampling at 9-11 weeks gestation may be used for gender determination and direct DNA analysis for the 21-hydroxylase gene CYP21.186,189,197 This test is associated with a 1-4% risk of miscarriage and 2% risk of limb defects. An alternative is karyotyping and DNA analysis or measuring androstenedione and 17-OH progesterone levels in amniotic fluid at 16-18 weeks of gestation after dexamethasone has been withheld for 5 days.197 Side effects of dexamethasone therapy are potentially significant, including excessive weight gain, severe striae with scarring, edema, irritability, gestational diabetes mellitus, hypertension, and gastrointestinal intolerance.189,198 In affected pregnancies, dexamethasone may be lowered to 0.75 to 1.0 mg/day in the second half of pregnancy to decrease maternal side effects while avoiding fetal virilization.198 Primary Hyperaldosteronism During Pregnancy Primary hyperaldosteronism rarely has been reported in pregnancy,199-203 and is most often caused by an adrenal adenoma. There are rare reports of glucocorticoid-remediable hyperaldosteronism in pregnancy.204 The elevated aldosterone levels found in patients are similar to those in normal pregnant women, 16
  17. 17. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy but the plasma renin activity is suppressed.199-202 Moderate to severe hypertension is seen in 85%, proteinuria in 52%, and hypokalemia in 55%,203 and symptoms may include headache, malaise, and muscle cramps.205 Placental abruption and preterm delivery are risks.206 Progesterone has an antimineralocorticoid effect at the renal tubules, and the hypertension and hypokalemia may ameliorate during pregnancy.207 The physiologic rise in aldosterone during pregnancy overlaps the levels seen in pri- mary aldosteronism, making diagnosis difficult.133,203 Suppressed renin in the set- ting of hyperaldosteronism is diagnostic. Salt loading tests may be used to diagnose hyperaldosteronism, but there are potential fetal risks and no normative data.200 If baseline and suppression testing are equivocal, or radiologic scanning does not suggest unilateral disease, patients may be treated medically until delivery to allow more definitive investigations.201 Spironolactone, the usual nonpregnant therapy, is contraindicated in pregnancy as it crosses the placenta and is a potent antiandro- gen which can cause ambiguous genitalia in a male fetus.202 There is no published experienced with the use during pregnancy of dplerenone, the new aldostgerone re- ceptor antagonist. Surgical therapy may be delayed until postpartum if hypertension can be controlled with agents safe in pregnancy, such as amiloride, methyldopa, la- betolol, and calcium channel blockers.201,207,208 Potassium supplementation may be required, but as noted above, the hypokalemia may ameliorate in pregnancy be- cause of the antikaliuretic effect of progesterone. Both hypertension and hypokalemia may exacerbate postpartum due to removal of the progesterone effect.209,210 Pheochromocytoma in Pregnancy Exacerbation of hypertension is a typical presentation of pheochromocytoma in nonpregnant patients, but during pregnancy is frequently mistaken for pregnancy-induced hypertension or preeclampsia.211 The prevalence is estimated at 1 in 54,000 pregnancies.212 As the uterus enlarges and an actively moving fetus compresses the neoplasm, maternal complications such as severe hypertension, hemorrhage into the neoplasm, hemodynamic collapse, myocardial infarction, cardiac arrhythmias, congestive heart failure, and cerebral hemorrhage may occur. Extra-adrenal tumors which occur in 10%, such as in the organ of Zuckerkandl at the aortic bifucation, are particularly prone to hypertensive episodes with changes in position, uterine contractions, fetal movement, and Valsalva maneuvers.213 Unrecognized pheochromocytoma is associated with a maternal mortality rate of 50% at induction of anesthesia or during labor.214,215 There is minimal placental transfer of catecholamines,216,217 likely due to high placental concentrations of catechol-O-methyltransferase and monoamine oxidase.216,218 Adverse fetal effects such as hypoxia are a result of catecholamine-induced uteroplacental vasoconstriction and placental insufficiency,219-221 and of maternal hypertension, hypotension, or vascular collapse. As always, diagnosis of pheochromocytoma requires a high index of suspicion. Pre- conception screening of families known to have MEN 2 with RET proto-oncogene is essential. Patients with MEN 2A are more likely to have paroxysmal hypertension and have higher rates of bilateral neoplasms than those with sporadic pheochro- mocytoma.222 Examination for associated evidence for MEN2 may be difficult in pregnancy, with the expected pregnancy alterations in calcium, PTH, and calcitonin. Clinical thyroid examination should be done, with fine needle aspiration of any nod- ules so that overt medullary carcinoma can be treated immediately. Individuals with neurofibromatosis,223 von Hipple-Lindau disease,224 or retinal angiomatosis should also be screened for pheochromocytomas prior to pregnancy. The diagnosis should be considered in pregnant women with severe or paroxysmal hypertension, particularly in the first half of pregnancy or in association with ortho- static hypotension or episodic symptoms of pallor, anxiety, headaches, palpitations, chest pain, or diaphoresis. Symptoms may occur or worsen during pregnancy be- 17
  18. 18. Chapter 2. Pituitary and Adrenal Disorders of Pregnancy cause of the increased vascularity of the tumor and mechanical factors such as pres- sure from the expanding uterus or fetal movement.220 Laboratory diagnosis of pheochromocytoma is unchanged from the nonpregnant state as calecholamine metabolism is not altered by pregnancy per se.225 If possible, methyldopa and labetolol should be discontinued prior to the investigation as these agents may interfere with the quantification of the catecholamines and VMA.226 Provocative testing should be avoided because of the increased risk of maternal and fetal mortality. Tumor localization with MRI, with high intensity signals noted on T2-weighted images, provides the best sensitivity without fetal exposure to ionizing radiation. Metaiodobenzylguanidine and [18F]-dopamine-labeled positron emission tomography scans are contraindicated in pregnancy, but may be used postpartum to assess extra-adrenal disease. Differentiation from preeclampsia is generally simple. The edema, proteinuria, and hyperuricemia found in preeclampsia is absent in pheochromocytoma. Plasma and urinary catecholamines may be modestly elevated in preeclampsia and other serious pregnancy complications requiring hospitalization, though they remain normal in mild preeclampsia or pregnancy-induced hypertension.227 Catecholamine levels are 2- to 4-times normal after an eclamptic seizure.228 Initial medical management involves α-<61485>blockade with phenoxybenzamine, phentolamine, prazosin, or labetolol. All of these agents are well-tolerated by the fetus, but phenoxybenzamine is considered the preferred agent as it provides long- acting, stable, non-competitive blockade.220 Phenoxybenzamine is started at a dose of 10 mg twice daily, with titration until the hypertension is controlled. Placental transfer of phenoxybenzamine occurs,229 but is generally safe.230,231 If hyperten- sion remains inadequately controlled, metyrosine has also been used successfully to reduce catecholamine synthesis in a pregnancy complicated by malignant pheochro- mocytoma,232 but may potentially adversely affect the fetus. Beta blockade is re- served for treating maternal tachycardia or arrhythmias which persist after full α- blockade and volume repletion. Beta blockers may be associated with fetal bradycar- dia and with intrauterine growth retardation, when used early in pregnancy.225,233 All of these potential fetal risks are small compared to the risk of fetal wastage from unblocked high maternal levels of catecholamines. Hypertensive emergencies should be treated with phentolamine (1-5 mg) or nitroprusside, although the latter should be limited because of fetal cyanide toxicity. The timing of surgical excision of the neoplasm is controversial and may depend on the success of the medical management and the location of the tumor. As noted above, pressure from the uterus, motion of the fetus, and labor contractions are all stimuli that may cause an acute crisis, particularly in patients with a tumor at the organ of Zuckerkandl. In the first half of pregnancy, surgical excision may proceed once adequate α-blockade is established, although there is a higher risk of miscar- riage with first trimester surgery. In the early 2nd trimester, abortion is less likely and the size of the uterus will not make excision difficult. If the pheochromocytoma is not recognized until the second half of gestation, increasing uterine size makes surgical exploration difficult. Successful laparoscopic excision of a pheochromocytoma in the 2nd trimester of pregnancy has been described.234 Other options include combined cesarean delivery and tumor resection or delivery followed by tumor resection at a later date. Delivery is generally delayed until the fetus reaches sufficient maturity to reduce postpartum morbidity, providing successful medical management exists. Although successful vaginal delivery has been reported,235 it has been associated with higher rates of maternal mortality than cesarean section. Labor may result in uncontrolled release of catecholamines secondary to pain and uterine contractions.236 Severe maternal hypertension may lead to placental ischemia and fetal hypoxia. However in the well-blocked patient, vaginal delivery may be possible using intensive pain management with epidural anesthesia and avoidance of mechanical compression, employing techniques of passive descent and instrumental delivery. There is no available information regarding the impact of maternal use of phenoxy- 18
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