Comparative stereological study on zonation and cellular composition of adrenal glands of normal and anencephalic human fetuses. I. Zonation of the gland.

Comparative stereological studies were performed on zonation of adrenal glands in 10 anencephalic and 11 normal fetuses, aged between 24 and 39 postovulatory weeks. The development of adrenal fetal zone (FZ) is the main factor responsible for normal adrenal gland growth during the intra-uterine life. At the end of fetal period volume of this zone attains over 8200 mm3 and constitutes 69-70% of the total gland volume, while respective values for zona glomerulosa (ZG), zona fasciculata (ZF) and medulla (M) are 1665 mm3 (14%), 833 mm3 (7%) and 1071 mm3 (9%). These data were in striking contrast with those found in adrenals of anencephalic fetuses, in which volume of the gland attained only ca 35% of that in normal fetuses. In the oldest anencephalic fetus studied (39 weeks) the volume of the fetal zone was 962 mm3 (ca 8-folds lower than in normal fetus) comprising only 25% of the total gland volume. For the remaining zones the values were: ZG-1501 mm3 (ca 90% of the normal value and 39% of the total gland volume); ZF-770 mm3 (ca 92% and 20% respectively), and M-539 mm3 (ca 50% and 14%, respectively). This stereological study provides the first systemic description of the development of adrenal gland of anencephalic fetuses in comparison with the normally developing gland. Moreover, evidence is given that the growth of adrenal medulla is also retarded in anencephaly while the growth of the zona glomerulosa remains rather unaffected.