Thyroid function studies in normal pregnant Tanzanian women.

Iodine deficiency is well known as a cause of several disorders such as endemic goiter and cretinism, along with a wide spectrum of psychoneurologic development disorders including endemic mental deficiency, which are generally correlated with damage to the fetus. Since as much as 40% of the Tanzanian population is at risk for iodine deficiency disorders (IDD) because they live in iodine-deficient areas, and although the effects of iodine deficiency on human reproduction in Tanzania have not been objectively studied, it is estimated that there are approximately 600,000 cretins and cretinoids in the country as a result of IDD. As a baseline study for future research on iodine deficiency and its effects on human reproduction in Tanzania, we assayed serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and free thyroxine (FT4) in 93 clinically euthyroid pregnant women and 34 nonpregnant women as controls. Pregnancy was accompanied by significantly increased levels of total T3 and T4, decreased FT4, and increased TSH concentration in serum. However, biochemical euthyroidism (assessed by FT4 and basal TSH) was demonstrated in almost all (99%) of the pregnant subjects in conformity with most of the previous findings elsewhere. We conclude that pregnant Tanzanian women residing in areas without iodine deficiency experience changes in biochemical parameters of thyroid function similar to their counterparts in other places.