Chapter-20 Thyroid Disorders with Pregnancy

BOOK TITLE: Management of High-Risk Pregnancy—A Practical Approach

1. Aggarwal Kiran
Publishing Year
Author Affiliations
1. Lady Hardinge Medical College and SSK Hospital New Delhi, India, Municipal Corporation of Delhi, Delhi, India, Lady Hardinge Medical College and SSK Hospital, New Delhi, Municipal Corporation of Delhi, Member, Child Welfare Committee, Delhi, India, North Delhi Municipal Corporation Medical College and Hindu Rao Hospital, New Delhi, India, Hindu Rao Hospital, MCD, Delhi, D11/2, 14 Rajpur Road, Civil Lines, Delhi 110054
Chapter keywords


Thyroid disorders are common endocrine disorders in young women and difficult to diagnose clinically in pregnancy because of overlap of normal signs and symptoms of pregnancy with those of thyroid diseases. Human chorionic gonadotrophin has some thyrotrophic function, so it stimulates thyroid receptors causing increase in free T4 levels and decrease in TSH levels particularly in first trimester. For thyroid functions in pregnancy, free T4 T3 and TSH should be used and trimester specific range should be considered. During first trimester fetus is dependent on maternal T4 for its requirements as fetal thyroid is not active and maternal hypothyroxinemia or iodine deficiency at this time can affect fetal brain development. In pregnancy and lactation, 200–300 µg/day of iodine is needed. Medical treatment is of choice in hyperthyroidism. Propylthiouracil and methimazole both can be used but former is used in first trimester preferably. In hyperthyroidism, maternal levels of free T4 should be maintained in the upper nonpregnant reference range with treatment. Both maternal and fetal hypothyroidism are known to have serious adverse effects on the fetus. Autoimmune thyroiditis is the most common cause of hypothyroidism in pregnancy. If hypothyroidism is first detected in pregnancy rapid institution of thyroxine should be done to normalize thyroid levels otherwise neurological functions of the fetus are jeopardized. In subclinical hypothyroidism, treatment with thyronine improves obstetrical outcome. Fine needle aspiration cytology should be performed for single or dominant thyroid nodule larger than 1 cm in pregnancy. If these nodules are found to be malignant or rapidly growing, surgery should be offered in the second trimester without interrupting pregnancy. Universal screening for thyroid disease is not recommended at present but case finding in the high risk group for thyroid dysfunction should be done.

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