Hypothyroidism, Fertility and Pregnancy

Abstract

Pregnancy has a profound effect on the thyroid gland and its function. In iodine-replete countries, the gland size has been found to increase by 10% during pregnancy, and in areas of iodine deficiency, the gland size increases by 20%–40%. The prevalence of hypothyroid‐ ism during pregnancy is estimated to be 0.3–0.5% for overt hypothyroidism and 2–3% for subclinical hypothyroidism. Worldwide, iodine deficiency remains one of the leading causes of both overt and subclinical hypothyroidism. However, there are many other causes of hy‐ pothyroidism during pregnancy, including autoimmune thyroiditis, the most common or‐ ganic pathology [1]. Other causes include the following: thyroid radioiodine ablation (to treat hyperthyroidism or thyroid cancer), hypoplasia and/or agenesis of the thyroid gland, surgery (for thyroid tumors and, rarely, central hypothyroidism, including lymphocytic hy‐ pophysitis or ectopic thyroid) and some drugs, such as rifampin and phenytoin, which can alter thyroid metabolism [2].