Background: Low energy availability (LEA) in female athletes can result in HPG axis suppression. Basic military training (BMT) is physically arduous and associated with amenorrhoea and low-trauma fractures. We hypothesised that women undergoing BMT would demonstrate evidence of LEA and suppressed HPG function.
Design: Prospective study of 61 women undertaking 11-month BMT. Subjects acted as their own controls at baseline (all measures). Body composition measurement (DXA) was repeated after 3, 7 and 11 months; fasting blood (glucose, insulin (for homeostatic model of insulin resistance, HOMA2), leptin, inhibin B, estradiol, anti-Müllerian hormone (AMH), and FSH) after 7 and 11 months, and dynamic 1-h 10 µg GnRH test measuring LH and FSH after 7 months. Menstruation and ovulation were assessed in non-contraceptive pill-users (n=22) using diaries and weekly urinary progesterone : creatinine ratio, respectively.
Results: 52 women, aged 24.0±0.3 years, completed the study. Fat mass decreased 0.8 kg from baseline to month 3, increased 1.8 kg to month 7 and reverted to baseline by month 11 (P<0.001). Fat-free mass did not change (P=0.13). HOMA2 and leptin increased (both P<0.001), as did estradiol and inhibin B (P<0.05) while AMH was unchanged (P=0.6) (Table). Maximum and area-under-the-curve fold-responses of LH and FSH to GnRH were suppressed after 7 months (both P<0.001). Findings were unaffected by contraceptive use (effect × time P=0.8). Seven participants (32%) became oligo/amenorrhoeic. 87% of regular (2335d) cycles were anovulatory.
|Baseline||7 months||11 months|
|Inhibin B, pg.ml−1||26.8±10.9||54.0±30.8*||42.3±27.6*|
Conclusion: Evidence of adiposity-related adaptation suggests non-LEA stressors contributed to HPG axis suppression and follicular dysgenesis. Further studies are required to deliniate causes of reproductive dysfunction and associated pathology in military women.