Sex-related hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axis adaptation during military training

Gifford, RM, O’Leary, TJ, Knight, RL, Wardle, SL, Doig, CL ORCID: https://orcid.org/0000-0001-9694-4230, Anderson, RA, Greeves, JP, Reynolds, RM and Woods, DR, 2025. Sex-related hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axis adaptation during military training. Journal of Applied Physiology, 138 (1), pp. 13-21. ISSN 8750-7587

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Abstract

Reproductive endocrine function adapts to psychological, environmental, and energy-associated stressors. Multistressor environments upregulate hypothalamic-pituitary-adrenal (HPA) axis, causing suppression of the hypothalamic-pituitary-gonadal (HPG) axis, but it is not known if this pattern or its magnitude is sex biased. We compared HPG and HPA axis activity in 9 men and 34 women undergoing Army training. One-hour low-dose gonadorelin and Synacthen tests were conducted at 1 and 29 wk, measuring gonadotrophins and cortisol. Cortisol was measured from hair every 3 mo. Morning and evening salivary cortisol and psychometric questionnaires were measured at six timepoints. Sexes were compared over time by two-way ANOVA. Gonadotrophin responses were significantly higher in women than men in week 1, but no sex difference was seen at week 29 (no significant sex × time interaction). Week 1 cortisol response was higher among men, but week 29 cortisol response was higher among women (sex × time F(1,44) = 18.0, P < 0.001). Hair cortisol was higher among women than men beforehand, not different between sexes during the first 3 mo, and significantly higher among women during training months 5–11 (F(3,15) = 3.25, P = 0.024). Morning salivary cortisol was higher among women in weeks 8 and 14, but higher among men in week 29 (F(4,76) = 4.0, P = 0.005). No differences were seen in evening salivary cortisol. Psychometrics did not change or differ between sexes. HPA axis responses to military training were greater among women than men. HPG axis responses suggest greater downregulation among women. These findings will enable equitable and individualized management of people undergoing periods of intensive physical stress.

Item Type:	Journal article
Publication Title:	Journal of Applied Physiology
Creators:	Gifford, R.M., O’Leary, T.J., Knight, R.L., Wardle, S.L., Doig, C.L., Anderson, R.A., Greeves, J.P., Reynolds, R.M. and Woods, D.R.
Publisher:	American Physiological Society
Date:	January 2025
Volume:	138
Number:	1
ISSN:	8750-7587
Identifiers:	Number Type 10.1152/japplphysiol.00691.2024 DOI 39589823 PubMed ID 2554857 Other
Rights:	© 2025 The Authors. Licensed under Creative Commons Attribution CC-BY 4.0. Published by the American Physiological Society.
Divisions:	Schools > School of Science and Technology
Record created by:	Melissa Cornwell
Date Added:	13 Jan 2026 16:21
Last Modified:	13 Jan 2026 16:21
URI:	https://irep.ntu.ac.uk/id/eprint/55035

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