Early diagnosis and effective treatment of thyroid diseases during pregnancy are the greatest priority. A delay in treatment can have severe adverse effects on the mother and unborn child.
Thyroid-stimulating hormone (TSH) and T4 levels are checked as the first test to evaluate thyroid function during pregnancy. TSH levels are elevated, and T4 levels are depleted in hypothyroidism. About 2.5% of pregnant women experience it. Hypothyroidism, if left untreated, can cause neurological issues and developmental delays. 0.1-0.4% of pregnant women have hyperthyroidism. Graves' disease accounts for 80-85% of cases in pregnant women. Functional adenoma, thyroiditis, and thyrotoxicosis factitia are additional causes of hyperthyroidism in pregnant women besides Graves' disease (use of high-dose thyroxine hormone). Abortion, pre-eclampsia, premature birth, retardation in the baby's normal development, and intrauterine fetal death are possible outcomes if a pregnant woman with hyperthyroidism is not treated effectively.
Levothyroxine (LT4), used in treating hypothyroidism in pregnant women, should be started as soon as possible. During the follow-up period, it is appropriate to measure TSH every 6-8 weeks after the initiation of treatment. TSH levels should be maintained between 0.5 and 2.5 mU/L during the first trimester of pregnancy and between 0.5 and 2.5 mU/L during the second and third trimesters.
Medical therapy is the first line of treatment for hyperthyroidism during pregnancy. The goal of treatment is to maintain a serum fT4 level close to the upper limit of average values using the smallest effective dose of antithyroid medication. Due to potential side effects, treatment with propylthiouracil is preferred among antithyroid drugs. Propylthiouracil can be started at 100–150 mg per day. With 4-6 weeks of follow-up, the serum fT4 level to be used in the follow-up should be checked.