Rapid regression of fetal adrenal zone and absence of adrenal reticular zone in the marmoset

Developmental changes in plasma dehydroepiandrosterone (DHA) and in adrenal histology were studied in several marmoset species (Callithrix jacchus and Saguinus labiatus, nigricollis, and fuscicollis) to evaluate these primates as experimental models for the study of fetal adrenal zone regression. Newborn marmosets had a prominent fetal adrenal zone, plasma DHA levels above 1000 ng/dl, and plasma DHA sulfate (DHAS) levels of 140 μg/dl. The fetal zone regressed dramatically during the first week of life, paralleled by a marked decline in plasma DHA, the plasma DHA to cortisol ratio, and plasma DHAS. The adult marmoset, however, had no adrenal reticular zone and no evidence of adrenal DHA secretion; DHA levels in castrate adults were undetectable (<25 ng/dl). Thus, the marmoset represents the first example of a primate that has a regressing, DHA- and DHAS-secreting fetal adrenal zone but that does not subsequently develop a DHA-secreting adrenal reticular zone.