Female Reproductive, Adrenal, and Metabolic Changes during an Antarctic Traverse.

PURPOSE: To explore the effects of the first all-female transantarctic expedition on hormonal axes pertinent to reproductive and metabolic function.

METHODS: Six females (aged 28-36, BMI 24.2 ±0.97 kgm) hauled 80kg sledges 1700km in 61 days. Estimated average energy intake was 20.8 ± 0.103 MJ/day (4970 ±25 kcal/day). Whole and regional body composition was measured by DXA one and two months before and 15 days after, the expedition. Body fat was also estimated by skinfold and bioimpedance immediately before and after the expedition. Basal metabolic and endocrine blood markers and, after 0.25 mg dexamethasone suppression, 1-hour 10 μg Gonadorelin and 1.0 μg ACTH-(1-24) tests were completed, 39-38 days pre- and 4-5 and 15-16 days post-expedition. Cortisol was assessed in hair (monthly average concentrations) and saliva (5-point day curves and two-point diurnal sampling).

RESULTS: Average body mass loss was 9.37 ±2.31 kg (p<0.0001), comprising fat mass only; total lean mass was maintained. Basal sex steroids, corticosteroids and metabolic markers were largely unaffected by the expedition except leptin, which decreased during the expedition and recovered after 15 days, a proportionately greater change than body fat. LH reactivity was suppressed prior to and during the expedition, but recovered after 15 days, while FSH did not change during or after the expedition. Cortisol reactivity did not change during or after the expedition. Basal (suppressed) cortisol was 73.25 ±45.23 mmol/L before, 61.66 ± 33.11 mmol/L 5 days post- and 54.43 ±28.60 mmol/L 16 days post-expedition (p=0.67). Hair cortisol was elevated during the expedition.Maintenance of reproductive and HPA axis function in women following an extreme physical endeavor, despite energy deficiency, suggests high female biological capacity for extreme endurance exercise.