Lecture 14 Thyroid diseases in pregnancy
Thyroid diseases, such as hypothyroidism and hyperthyroidism, can occur during pregnancy and can have significant effects on both the mother and the fetus. Hypothyroidism, which is an underactive thyroid, is a common condition that occurs when the thyroid gland does not produce enough thyroid hormones. Symptoms of hypothyroidism can include fatigue, weight gain, cold intolerance, and constipation. Pregnant women with hypothyroidism are at an increased risk of miscarriage, preterm labor, and placental abruption. The condition can also affect the development of the fetus's brain and nervous system. Hyperthyroidism, which is an overactive thyroid, is a less common condition that occurs when the thyroid gland produces too much thyroid hormones. Symptoms of hyperthyroidism can include weight loss, increased appetite, tremors, and nervousness. Hyperthyroidism during pregnancy can lead to hypertension, preterm labor, and placental abruption. Thyroid dysfunction can be diagnosed through blood tests, and it's important to be treated properly during pregnancy to minimize the risk of complications. Treatment can include medication such as levothyroxine, and in some cases, radioactive iodine therapy or surgery. It's important for pregnant women to have their thyroid function tested early in pregnancy and for women who have known thyroid problems or a family history of thyroid disease to be closely monitored during pregnancy.
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Lecture 14 Thyroid diseases in pregnancy
- 2. Physiological changes of thyroid Thyroid Function in Pregnancy Increased TBG Increased total thyroxine, and T3 Free T4 and T3 remain unchanged BMR increases 15-20% above normal TSH is lower in first trimester (HCG effect) TSH does not cross the placenta Relative iodine deficiency Increase absorption of iodine In pregnancy thyroid function is tested by free T4 and TSH , total T3 T4 not to be used
- 3. Hypothyroidism CAUSES OF HYPOTHYROIDISM :
- 5. Hypothyroidism in pregnancy Incidence of 1 % Subclinical is more than overt (2 % vs 0.2 % ) Most common cause worldwide is iodine deficiency Most common cause In developed countries is autoimmune thyroiditis (hashimotos ) Treatment is needed for overt cases and maybe some subclinical cases with positive antibodies Serial thyroid function test is needed for hypothyroid cases in pregnancy every 4- 6 months using TSH and FREE T4 Aim of treatment is TSH less than 4 mmol/L
- 6. Possible complications of hypothyroidism Subclinical hypothyroidism seems to has no effect unless antibodies are positive (TPO positive ) where TSH is high but free T3 T4 is normal
- 7. Treatment by L-thyroxine Most widely prescribed treatment Category A 25-300 mcg If newly diagnosed in pregnancy started @ 1-2µg/kg/d or 100-150µg/d If previously hypothyroid dose increased by 25-40% Postpartum: • Decrease dose by 30% (if newly diagnosed) • Breast feeding is not contraindicated
- 8. Hyperthyroidism Incidence of 0.2 % Types : • Subclinical- low TSH normal FT3, FT4 • Overt- low TSH high FT4, FT3 • Physiological and Gestational hyperthyroidism (in cases where there is an excessive HCG ) Symptoms: Palmar erythema, emotional lability, vomiting, goiter, heat intolerance, exophthalmos, fail to gain weight Only overt needs treatment
- 9. Causes of hyperthyroidism Most common cause in child bearing age is GRAVES disease (autoimmune ) INTRINSIC THYROID DISEASE • Grave’s • Toxic nodule • Subacute thyroiditis EXOGENOUS THYROID HORMONE • Factitious • Therapeutic GESTATIONAL THYROTOXICOSIS (increased HCG) •Hyperemesis •GTD •Hydatidiform mole •Multiple gestations •Hydrops RARE •TSH producing pituitary tumour •Iodine deficiency •Struma ovarii
- 10. Symptoms
- 12. Antenatal treatment of new cases Detected in 1st trim- observe Persists in 2nd trim- t/t THIONAMIDES: 1. Propylthiouracil • Less readily crosses placenta • 50-150mg TDS • Category D • Side effects- m/c rash Fetal hypothyroidism Transient leukopenia (10%) Agranulocytosis (0.3-0.4%) discontinue t/t Hepatotoxicity (0.1-0.2%) Vasculitis
- 13. 2. Methimazole or carbimazole • 5-20mg BD • Crosses placenta readily • Category D • Methimazole embryopathy- Esophageal atresia, choanal atresia, cutis aplasia FETAL MONITORING: • 10% hypothyroidism • Clinical exam • USG • Cordocentesis • Selective Fetal blood sampling
- 14. treatment aims to maintain maternal fT3 and fT4 levels in the high/normal range Subtotal thyroidectomy rarely (retrosternal goiter causing airways obstruction , suspicion of malignancy ) Radioactive iodine ablation is contraindicated While Using drugs regular checks of maternal white cell count are necessary Both drugs cross placenta and present in breast milk (use the least effective dose )
- 16. Postpartum management Immunosuppression disappears postpartum Graves Relapse postpartum in 70 % (improve in late pregnancy ) TSH & freeT4 test at 6weeks post partum Lactating mother- • PTU & methimazole excreted in breast milk • PTU protein bound. Safer • Methimazole only at low doses (10-20mg/d)
- 17. Thyroid storm life-threatening (20-50 % mortality if untreated ) Acute exacerbation of hyperthyroidism, life threatening, hypermetabolic state Rare in pregnancy precipitated by sepsis, preeclampsia & anemia and labor Excessive sweating, pyrexia, tachycardia, atrial fibrillation, hypertension, hyperglycemia, vomiting, agitation and cardiac failure
- 19. Postpartum thyroiditis lymphocytic infiltration of gland High chances if high titers of Antibodies Phases- Hyperthyroid (1/3 will go into the second phase ) Hypothyroid (1/3 will have permeant hypothyroidism ) Hyperthyroidism usually doesn’t need treatment as its transient but hypothyroid phase needs thyroxine therapy )
- 20. Fetal thyroid disease Hypothyroidism or thyrotoxicosis can occur due to passage of maternal antibodies to the fetus over treatment of maternal hyperthyroidism by antithyroid drugs can lead to fetal hypothyroidism Fetal hyperthyroidism is more common and fetal monitoring to detect goiter , tachycardia or hydrops and IUGR is needed for women having antibodies even if euthyroid (women with positive antibodies who had ablation or total thyroidectomy before )