Objective Less than half of servicewomen report loss of menses during initial military training. However, self-reported menstrual status may not accurately reflect hypothalamic-pituitary-ovarian (HPO) axis suppression and may underestimate reproductive health consequences of military training. Our aim was to characterise HPO axis function during US Army Basic Combat Training (BCT) in non-hormonal contraceptive-using women and explore potential contributors to HPO axis suppression. Methods In this 10-week prospective observational study, we enrolled multi-ethnic women entering BCT. Trainees provided daily first-morning voided urine, and weekly blood samples during BCT. Urinary luteinising hormone, follicle stimulating hormone, and metabolites of estradiol and progesterone were measured by chemiluminescent assays (Siemens Centaur XP) to determine hormone patterns and luteal activity. We measured body composition, via dual-energy X-ray absorptiometry, at the beginning and end of BCT. Results Trainees (n=55) were young (mean (95% CI): 22 (22, 23) years) with average body mass index (23.9 (23.1, 24.7) kg/m2). Most trainees (78%) reported regular menstrual cycles before BCT. During BCT, 23 (42%) trainees reported regular menses. However, only seven trainees (12.5%) had menstrual cycles with evidence of luteal activity (ELA) (ie, presumed ovulation), all with shortened luteal phases. 41 trainees (75%) showed no ELA (NELA), and 7 (12.5%) were categorised as indeterminant. Overall, women gained body mass and lean mass, but lost fat mass during BCT. Changes in body mass and composition appear unrelated to luteal activity. Conclusions Our findings reveal profound HPO axis suppression with NELA in the majority of women during BCT. This HPO axis suppression occurs among women who report normal menstrual cycles. Data are available upon reasonable request.

中文翻译：

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在美国陆军基础战斗训练中，女性下丘脑-垂体-卵巢轴抑制很常见


目标 不到一半的女军人表示在最初的军事训练期间月经消失。然而，自我报告的月经状况可能无法准确反映下丘脑-垂体-卵巢（HPO）轴抑制，并且可能低估军事训练对生殖健康的影响。我们的目的是表征美国陆军基础战斗训练 (BCT) 期间未使用激素避孕药的女性的 HPO 轴功能，并探索 HPO 轴抑制的潜在因素。方法 在这项为期 10 周的前瞻性观察研究中，我们招募了参加 BCT 的多种族女性。在 BCT 期间，学员每天提供第一晨的排尿样本，并每周提供血液样本。通过化学发光测定（Siemens Centaur XP）测量尿液黄体生成激素、卵泡刺激素以及雌二醇和黄体酮的代谢物，以确定激素模式和黄体活性。我们在 BCT 开始和结束时通过双能 X 射线吸收测定法测量了身体成分。结果 受训者 (n=55) 很年轻（平均 (95% CI)：22 (22, 23) 岁），平均体重指数为 (23.9 (23.1, 24.7) kg/m2)。大多数学员 (78%) 在 BCT 之前报告月经周期规律。在 BCT 期间，23 名 (42%) 学员报告月经正常。然而，只有 7 名受训者 (12.5%) 的月经周期有黄体活动 (ELA)（即推定排卵）证据，且全部黄体期缩短。 41 名学员 (75%) 未表现出 ELA (NELA)，7 名 (12.5%) 被归类为不确定。总体而言，女性在 BCT 期间增加了体重和去脂体重，但减少了脂肪量。体重和成分的变化似乎与黄体活动无关。结论 我们的研究结果揭示了 BCT 期间大多数女性 NELA 对 HPO 轴产生了深刻的抑制。 这种 HPO 轴抑制发生在月经周期正常的女性中。数据可根据合理要求提供。