Age-related Changes in Dehydroepiandrosterone-sulfate in Black-and-gold Howler Monkeys (Alouatta caraya)

Abstract

Dehydroepiandrosterone-sulfate (DHEAS) is the most abundant steroid in humans and some nonhuman primates. This adrenal androgen contributes to immune enhancement, neuroprotection, and reproduction. In humans and apes, DHEAS levels increase before puberty, a phenomenon called adrenarche. However, a postnatal increase in the levels of these hormones is not apparent in cercopithecoids. In marmosets, DHEAS is only synthesized from female adrenal glands, if their ovarian function is compromised. However, DHEAS is poorly investigated among other platyrrhines. Our main objective was to test the influence of sex and age on fecal and serum DHEAS levels in black-and-gold howler monkeys ( Alouatta caraya ) under human care. We measured DHEAS levels in feces from 16 females and 21 males aged between 6 months and 26 years old and in serum from 27 of those animals using a commercial enzyme immunoassay kit. We found high levels of serum DHEAS in adult females, and DHEAS levels in fecal and serum samples were strongly and positively correlated. Fecal DHEAS levels showed a quadratic relationship with age, increasing from infancy to adulthood, then declining in older adults. There was no significant effect of sex, although females had a greater range than males. The postnatal increase in DHEAS levels in howler monkeys is like that of apes and humans, while the large variation in DHEAS levels among adult females suggests that, as in marmosets, DHEAS may be important for female howler monkey reproduction. This pattern highlights the importance of comparative studies to investigate the biological function of DHEAS in evolution. Graphical Abstract

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