Coupling of Adrenal and Gonadal Hormones: Potential Relationship to Occupational Demand

Abstract

The positive coupling hypothesis describes the hypothalamic-pituitary-adrenal and -gonadal systems as parallel, cooperative processes that represent joint calibration to meet internal, and/or environmental, demands. We recently tested this hypothesis in Naval Special Warfare (NSW) personnel and found positive coupling between the adrenal hormones, cortisol (CORT) and dehydroepiandrosterone (DHEA), and the gonadal hormone, testosterone (TESTO). PURPOSE: To test the positive coupling hypothesis in Explosive Ordnance Disposal (EOD) personnel; a specialized military population whose mission is to ensure that hazardous explosives are rendered safe for unit preservation and security. METHODS: Active duty U.S. Navy EOD operators (N = 64; mean ± SD age: 34 ± 6.0 years) self-collected saliva samples in a non-deployed, free-living setting on 2 consecutive weekdays at wake, wake + 30 min, wake + 60 min, 1600, and 2100 (10 samples total). Exclusion criteria included use of any anabolic supplements within the last 3 months. Coupling hypotheses (associations between CORT, DHEA, and TESTO summary parameters) were tested with Pearson product-moment correlation analyses. Established summary parameters were determined for each hormone: highest morning value, area under the curve (with respect to ground [morning values]), and averages of morning and evening values, respectively. RESULTS: DHEA was positively coupled with TESTO (r range: .28-.61, p < .05) and also with CORT (r range: .50-.57, p < .05) throughout the day. Positive coupling between CORT and TESTO was only observed in the evening (r =.32, p = .014). CONCLUSION: This study partially replicated our prior report in NSW personnel, which demonstrated that DHEA positively coupled with TESTO as well as CORT. The evening association of TESTO and CORT is also consistent with our previous findings and likely indicative of homeostatic processes. Unlike the previous study, however; the morning values of TESTO and CORT were not coupled in the present study. This inconsistency could potentially be explained by a warfighter’s specific operational demands. For example, positive coupling may be adaptive for duties that include direct engagement with the enemy. In contrast, uncoupling may be more conducive to ensuring unit safety and security.