The gonadotrophic response of Royal Marines during an operational deployment in Afghanistan

Abstract

Military training has been associated with changes in the hypothalamic-pituitary-gonadal axis consistent with central hypogonadism. Often such changes have been associated with body mass loss, though sleep deprivation and other psychological stress may also contribute. The effects of deployment in a combat zone on the hypothalamic-pituitary-gonadal axis in military personnel are not known. The objective was to investigate the hypothalamic-pituitary-gonadal axis in male military personnel deployed in Afghanistan. Eighty-nine Royal Marines were investigated pre-deployment, following 3 months in Afghanistan and following 2 weeks mid-tour leave. Testosterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), luteinising hormone (LH), 17-hydroxyprogesterone, androstenedione (AD) and insulin were assayed and body mass recorded. The results showed that body mass (kg) dropped from 83.2 ± 9.2 to 79.2 ± 8.2 kg during the first 3 months of deployment (p < 0.001). Total testosterone did not change, but SHBG increased (30.7 ± 9.7 vs. 42.3 ± 14.1 nmol/L, p < 0.001), resulting in a significant (p < 0.001) fall in calculated free testosterone (435.2 ± 138 vs. 375.1 ± 98 pmol/L). Luteinising hormone and FSH increased by 14.3% (p < 0.001) and 4.9% (p = 0.003) respectively. Free testosterone, SHBG, LH and FSH returned to baseline following 2 weeks of mid-tour leave. Androstenedione (AD) decreased by 14.5% (p = 0.024), and insulin decreased by 26% (p = 0.039), over the course of deployment. In this study of lean Royal Marines, free testosterone decreased during operational deployment to Afghanistan. There was no evidence to suggest major stress-induced central hypogonadism. We postulate that reduced body mass, accompanied by a decrease in insulin and AD synthesis, may have contributed to an elevated SHBG, leading to a decrease in free testosterone.

Effects of deployment on diet quality and nutritional status markers of elite U.S. Army special operations forces soldiers

“…One participant sustained a combat related injury and did not complete the deployment. The changing and often unpredictable nature of Soldier schedules and personnel assignments is common before, during, and after operational deployment and a similar pattern of loss to follow-up has been reported in previous deployment studies [7, 9]. Of the 50 participants with markers of nutritional status at baseline and post-deployment, all participants completed a food frequency questionnaire (FFQ) and background questionnaire at baseline and 33 also completed a FFQ and follow-up questionnaire upon return from deployment.…”

Sex differences in the physical performance, physiological, and psycho‐cognitive responses to military operational stress

“…Military operational stress can suppress the HPG axis in men (i.e. decreased testosterone and oestradiol, and increased sex hormone binding globulin [SHBG]), and over-activate the HPA axis (Friedl et al, 2000;Gomez-Merino, Chennaoui, Drogou, & Guezennec, 2004;Hill et al, 2015;Nindl et al, 2007aNindl et al, , 2007bO'Leary et al, 2020;Ofsteng et al, 2020). Although the independent effects of individual operational stressors on HPG and HPA axis function are less well known, and there are likely interactive effects in a multi-stressor environment, low energy availability appears to be primary driver of impaired HPG and HPA axis function, with sleep deprivation and psychological stress likely contributory factors (Opstad et al, 1984;Opstad & Aakvaag, 1982;Opstad & Aakvaag, 1983;O'Leary et al, 2020).…”

“…Studies reporting sex differences in energy expenditure and body composition in response to military operational stress have all been conducted over short‐term periods of up to 7 days. Based on male data, longer term military operational stress, including career courses and deployment ranging from 3 weeks to 3 months, is also associated with increased energy expenditure, body mass loss, and changes in endocrine status (Friedl et al, 2000; Henning et al, 2014; Hill et al, 2015; Nindl et al, 2007a; Ojanen et al, 2018; Margolis, Rood, Champagne, Young, & Castellani, 2013; Morgan et al, 2000), but not all (Farina et al, 2017). Similar metabolic disturbances, notably decreased IGF‐I and leptin, and decreased thyroid hormone concentrations, have also been reported over shorter periods of operational stress lasting one week or less in men (Gomez‐Merino, Chennaoui, Drogou, Bonneau, & Guezennec, 2002; Karl et al, 2017; Kyrolainen et al, 2008; Opstad, Falch, Oktedalen, Fonnum, & Wergeland, 1984).…”

Anabolic hormone profiles in elite military men

“…12 These hormones are also routinely monitored to gauge training adaptations and optimize performance in competitive athletes. 10,13 Although some work has documented acute anabolic hormone responses in military settings, 14,15 no published research has established daily, free-living profiles of military members. This creates a critical knowledge gap, given that military members are a unique population with elevated risk of occupational stress, 16 sleep disruption, 17 trauma, 18 and associated health consequences.…”

“…19 Some anabolic hormones are known to counteract such risks. For instance, military deployment erodes free testosterone concentrations, 15 while both endogenous 14 and exogenous DHEA (a testosterone precursor) buffer stress profiles during military training, 20 either through steroidogenic or independent neuroactive pathways. Likewise, sleep disruption-a pervasive military health challenge 17 -is linked to reduced testosterone concentrations 21 and Anabolic Hormone Profiles 5 compromised metabolic profiles, even in young men.…”