We recently established daily, free-living profiles of the adrenal hormone cortisol (Cort), the (primarily adrenal) anabolic precursor dehydroepiandrosterone (DHEA), and the (primarily gonadal) anabolic hormone testosterone (Testo) in elite military men. A prevailing view is that adrenal and gonadal systems reciprocally modulate each other; however, recent paradigm shifts prompted the characterization of these systems as parallel, cooperative processes (i.e., the “positive coupling” hypothesis).
PURPOSE: To test the positive coupling hypothesis in elite military men by evaluating associations between adrenal and gonadal biomarkers across the day.
METHODS: Fifty-seven healthy, active duty men (mean ± SE age = 33.4 ± 1.0 yr) self-collected salivary hormone samples in a nondeployed, free-living setting on two consecutive midweek workdays upon waking, +30 min, +60 min, 1600, and 2100 (10 samples total). Hypotheses were tested using correlational and linear regression models.
RESULTS: DHEA was positively coupled with Cort (r range: 0.28 - 0.30, all p < .05) as was Testo (r range: 0.43 - 0.59, all p < .01). Anabolic processes (i.e., DHEA, Testo) were also positively and reliably coupled across the day (r range: 0.31 - 0.39, all p < .05). In multivariate models, DHEA and Cort combined to account for 27 - 43% variance in Testo across the day, which was driven primarily by DHEA. DHEA and Testo modestly and less robustly predicted Cort concentrations; this was confined to the morning (area under the curve, ground F(3,51) = 2.9, p < .05), and Testo was the primary predictor (β = 0.38, p < .05).
CONCLUSION: To our knowledge, this is an unprecedented test of the positive coupling hypothesis in elite military men, a group at an elevated risk for chronic stress exposure. This study showed that adrenal and gonadal systems were positively coupled. Altogether, top-down co-activation of adrenal and gonadal hormone secretion may complement bottom-up counter-regulatory functions to foster anabolic balance and neuronal survival; hence, the “yin and yang” of adrenal and gonadal systems. This may be an adaptive process that is amplified by stress, competition, and/or dominance hierarchy.