Adrenarche in Comparative Perspective

Objectives: To addresses the hypothesis that human adrenarche is associated with extended juvenile brain development by comparing the timing of adrenal androgen production, brain development and lactation in a larger comparative mammalian context.

Methods: Findings from published literature are used to compare the developmental timing of adrenal androgens, brain glucose utilization and lactation in rats, rhesus macaques and humans.

Results: Comparison of the timing of androstenedione and progesterone production with developmental patterns of cortical glucose utilization and the timing of lactation in laboratory rats suggest that the rise and fall of adrenal hormone production centered on weaning plays a role in synaptogenesis during lactation as well as post weaning synaptic pruning. Comparison of the timing of cortical glucose utilization, DHEAS production and weaning in rhesus macaques also suggests that postnatally elevated levels of DHEAS may be related to patterns of synaptic formation and pruning centered on weaning. In contrast among humans, peak cortical glucose utilization occurs well after weaning and the rise in adrenal androgen production coincides with declining cortical glucose utilization with the onset of the juvenile stage.

Conclusions: Compared to rats and macaque, in humans the energetic demands of brain development and increased production of adrenal androgens are divorced from the timing of lactation, while the timing of adrenarche and brain development are still associated. Thus the neuroprotective effects of DHEAS may protect synaptic plasticity in metabolically active parts of the brain starting approximately at the age of 7, promoting prolonged development of the human prefrontal cortex.