Higher short-term exercise-associated reproductive, psychological and bone health-related outcomes have been reported in women than men, although the reasons for this are poorly understood. The first, all-female transantarctic expedition provided a unique opportunity to perform an observational study examining concurrent effects of extreme exercise on pertinent hormonal axes to reproductive dysfunction and associated pathology. Body composition was measured by dual-energy xray absorptiometry (DXA) one and two months before and 15 days after the expedition. Basal metabolic and endocrine markers and 1-hour dynamic adrenal and pituitary gonadotroph tests, were conducted before, and 45 and 1516 days after the expedition. Monthly hair cortisol was measured before and during the expedition. Basal bone turnover markers (BTMs) and high-resolution peripheral quantitate computerised tomography (HRpQCT) were assessed before and after the expedition. Six women (median (range) 32.7 (28.636.1) years) hauled 80 kg sledges 1700 km in 61 days, becoming the first all-female team to complete an Antarctic traverse. Mean (SD) weight loss was 9.37 (2.31) kg, entirely constituting fat mass; lean mass was unchanged. Basal sex steroids, corticosteroids and metabolic markers were largely unaffected by the expedition, except leptin and vitamin D, which fell during the expedition and recovered after 11 days. LH reactivity was suppressed prior to and during the expedition, recovering after 11 days, while FSH did not change during or after the expedition. Cortisol reactivity did not change during or after the expedition, although the HPA axis demonstrated marked sensitivity to central suppression. Monthly average cortisol was elevated during the expedition. BTMs revealed uncoupling before and during the expedition, resolving after 11 days. Tibial stiffness and fracture threshold were unchanged after the expedition. This study is unprecedented in women, demonstrating marked resilience in reproductive function, the HPA axis and bone, suggesting that female biological capacity for extreme endurance exercise is greater than anticipated.