hyperthyroidism in pregnancy

1. Hyperthyroidism in pregnancy
Moderator : Dr. Aravind
Presenter : Keerthana

2. Objectives
• Physiological changes in pregnancy
• Incidence
• Clinical features
• Pathogenesis
• Diagnosis
• Treatment
• Adverse effect
• Therapies not recommended

3. Physiological changes of thyroid during pregnancy
• TBG - increase ( hepatic synthesis is increased )
• TT4 AND TT3 - Increased to compensate for the rise
• FT3 - decreased
• FT4 - are altered less by pregnancy but do fall a little in 1st and 2nd
trimesters
• TSH - decreases in 1st trimester , increase in 2nd and 3rd trimester

5. Incidence
• 1 in 500 pregnancies
• 50% family history of autoimmune thyroid disease
• Most cases encountered in pregnancy have already been diagnosed and
will already be on treatment
• If thyrotoxicosis occurs for the first time in pregnancy it usually presents
late in 1st or early in 2nd trimester

6. Clinical features
Discriminatory features :
Weight loss
Exophthalmos
Tremors
Lid lag
Persistent tachycardia

7. Pathogenesis
95% : Graves’ disease
(Autoimmune disorder caused by TSH
stimulating harmone)
More rarely
Toxic multinodular goitre
Toxic adenoma
GTT
Subacute thyroiditis
Iodine, amiodarone or lithium therapy
Choriocarcinoma
Molar pregnancy

8. Screening for maternal thyroid antibodies
• Graves’ disease- with Fetal or neonatal hyperthyroidism in previous
pregnancy
• Active Graves’ disease being treated
• Euthyroid or have undergone ablative therapy and have Fetal tachycardia or
IUGR
• Chronic thyroiditis without goitre
• Fetal goitre on ultrasound
• Screening for neonatal thyroid antibodies

9. Diagnosis
• Overt - raised FT4 or FT3 , decreased TSH
• Subclinical - decreased TSH , normal FT3 and FT4

10. Treatment of hypothyroidism is not required in
• Transient subclinical hyperthyroidism- in first trimester as it is
considered to be a normal physiological finding
• hCG mediated overt hyperthyroidism : as it is transient and mild
• Hyperemesis gravidarum associated hyperthyroidism

11. Effect of thyrotoxicosis on pregnancy
• Exacerbations : may occur in 1st trimester
• Improvement and a lower requirement for antithyroid treatment during 2nd
and 3rd trimester

12. Aim of treatment
• Control the thyrotoxicosis
• Maintain optimal control with the lowest dose of antithyroid medication
• Monitoring
• The women should be clinically euthyroid
• FT4 at the upper end of normal range
• TFT every 4 week till TSH and FT4 are within normal, every trimester thereafter.

13. Treatment
• PROPYL THIOURACIL - blocks the oxidation of iodine in the thyroid gland :
prevents synthesis of T4 and T3
• Dose 150-400mg initially (4-6 weeks) and maintain with 50-150mg
• METHIMAZOLE - blocks the organification of iodine : decreases thyroid
harmone production
• Dose 5-15mg daily
In one report of 77 newborns of euthyroid mothers treated with PTU or methimazole, there were no significant differences in TSH
concentrations measured in cord blood at birth [15]. However, compared with control neonates who were not exposed in utero to thionamides,
mean cord TSH levels were higher in neonates exposed to PTU but not methimazole
Low thyroid function at birth is found in approximately one-half of neonates whose mothers received PTU or methimazole during pregnancy
and who had serum T4 concentrations within the normal (nonpregnant) range [4]. In spite of these observations, two studies reported that the
intelligence quotient (IQ) scores of children who were exposed to thionamides in utero (but were euthyroid at birth) were normal

14. • Pre treatment evaluation - neutrophil count less than 1000cells or elevated
liver transaminase ( more than 5 fold ) prior to initiating PTU
• Diagnosed before pregnancy :
• Surgery but has complication if hypocalcemia and hypothyroidism
• If already on treatment with methimazole then after careful monitoring of
TFT tests weekly then monthly then the drug to be discontinued if normal
TSH AND TRab are negative
• Switch to PTU before trying to conceive

15. • Diagnosed during pregnancy : PTU can be continued or switched back to methimazole at 16
weeks. Risk is can cause Fetal hypothyroidism but the pro is it is less metabolised in the liver
hence less hepatotoxicity
• Diagnosed after first trimester : symptomatic moderate to severe hyperthyroidism should take
methimazole
• Initial dosing
• PTU 50mg two to three times daily
• Methimazole 5 to 10 mg daily
• Carbimazole 5 to 15mg daily

16. Adverse effects
• PTU associated liver failure
• If tolerated and no adverse side effect then switch to methimazole in
second trimester
• Carbimazole rarely can cause neutropenia and agranulocytosis and
aplasia cutis
• Thionamide intolerance is present then surgery can be considered as
radioiodine therapy is contraindicated in pregnancy only when there is
increased risk of spontaneous abortion or premature delivery.
• Prior to thyroidectomy she needs to be treated with beta blockers and
pottassium iodide solution as it lowers the serum thyroid harmone
concentration acutely and decreased thyroid gland vascularity

17. During lactation
• Very little PTU and methimazole is excreted in breast milk safe for mothers
to breast feed while taking doses to PTU at or below 150mg/day and
methimazole 15mg/day
• High doses of antithyroid drug : thyroid function should be checked in
umbilical cord blood and at regular interval in the neonate.
• PTU associated hepatotoxicity , we consider methimazole. If the dose
exceeds :20mg daily then the infants should be assessed after one and
three months.
in a study of 139 mothers taking up to 20 mg methimazole daily, thyroid function, growth, and development of their breastfed
infants were normal [56]. Similar results were seen in a study of mothers taking PTU [57]. There has yet to be a report of
agranulocytosis or liver disease in an infant who was nursed by a woman taking PTU or methimazole.

18. Postpartum
• Measure TFT six weeks postpartum then every six weeks if an adjustment
dose is needed or every 4 months if TFT remain normal
• Postpartum hyperthyroidism maybe due to a relapse of Graves’ disease or
due to postpartum thyroiditis
in a study of 150 women with Graves' disease in remission after antithyroid drug therapy [59]. Of the 25 women who had a
subsequent pregnancy, 21 (84 percent) experienced a relapse, compared with 70 of 125 (56 percent) who did not have a pregnancy.
The risk of relapse appeared to be related to the postpartum period rather than the pregnancy itself as 20 of the 21 relapses
occurred four to eight months postpartum

19. Beta blockers
In early management of thyrotoxicosis.
Beta blockers in pregnant women with moderate to severe hyperthyroidism and hyperandergenic
symptoms
Metoprolol 25 to 50mg daily
Propranolol 20mg three to four times daily
Labetalol 100mg BD
They need to be tapered and discontinued within 2 to 6 weeks
For pregnant women with moderate to severe hyperthyroidism due to Graves’ disease, toxic
adenoma or toxic multinodular goitre thionamide remains the first choice of treatment.
Thionamide

20. Therapies not recommended
• Radio iodine- absolutely contraindicated. However studies shows that if
dome in first trimester before 8 to 10 weeks does not cause Fetal
hypothyroidism or congenital anomalies. Spontaneous pregnancy loss was
reported in a few cases.
• Thyroxine - little T4 crosses the placenta making it even more difficult to
determine the minimal dose of thionamide