Maturation of the Secretion of Thyroid Hormone and Thyroid-Stimulating Hormone in the Fetus

THYROID hormones have a vital role in fetal development in many species. The best studied are fetal rats and sheep, in which thyroid hormones have important physiologic functions, including stimulation of neural growth and pulmonary development. 1 What is known about pituitary and thyroid development in humans is based on histologic studies of abortuses or analysis of blood samples obtained in early pregnancy at hysterotomy for elective abortion or in later pregnancy at delivery. 2 3 4 5 However, the results derived from samples obtained at the time of hysterotomy or cesarean section may have been influenced by maternal fasting or transient hypotension, which could . . .