Thyroid Disease II: Hypothyroidism in Pregnancy

Abstract

Hypothyroidism affects between 2 and 12 per 1000 pregnancies. Symptoms in pregnancy are similar those encountered in the nonpregnant population, but may be attributed to the pregnancy itself. Thyroxine-binding globulin increases in pregnancy, leading to increased thyroxine levels in order to meet the metabolic needs of normal pregnancy. Routine screening is not recommended, and testing should be done using a targeted approach in women with symptoms or history of thyroid disease. Diagnosis is based upon the finding of an elevated serum TSH using population and trimester-specific ranges. Overt hypothyroidism, identified by high serum TSH and low free thyroxine, is associated with increased risk of pregnancy-related complications, and is treated with maternal thyroxine supplementation. Adequate iodine is necessary for fetal neurodevelopment, and women with iodine deficiency may present with a goiter, though it is important to distinguish it from other causes of thyroid enlargement, including malignancy. Postpartum thyroiditis is diagnosed infrequently, as only a small subset of women will demonstrate the classic biphasic presentation, Additionally, symptoms are often vague, nonspecific, and self-limited. Importantly, many women are at risk of eventually developing permanent hypothyroidism. This review contains 6 tables, and 48 references. Key words: euthyroid, goiter, overt hypothyroidism, postpartum thyroiditis, thyroixine binding globulin, thyroid peroxidase, thryroid nodules