Evolution of lactotropes in normal and anencephalic human fetuses

The presence of lactotropes in pituitaries removed from 15 normal fetuses, 1 normal premature infant, 3 normal infants, and 7 anencephalic fetuses or infants was studied by immunocytochemistry. These cells were first detected in normal fetuses at 18 weeks of gestation in both sexes. After 22 weeks of gestation, the number of cells increased sharply and regularly until term. Moreover, the cytoplasmic area of these cells increased significantly until term, but was decreased 4 and 5 months after birth. In all anencephalic fetuses, lactotropes were found; these cells were more numerous and often showed significantly greater cytoplasmic area than those in normal fetuses. A stimulatory effect of the fetal hypothalamus, therefore, is not essential for the development of this cell type.