Anovulation Is Common Among Women During U.S. Army Basic Combat Training

PURPOSE: Menstrual cycle changes are commonly reported by female trainees during 8 to 10 weeks of U.S. Army Basic Combat Training (BCT). Whether reported menstrual cycles changes reflect hypothalamic-pituitary-ovarian (HPO) axis suppression during BCT is unknown. HPO axis suppression can lead to poor bone health and increased injury risk. METHODS: Female trainees (n = 47) who were not using hormonal contraceptives, provided fasted, rested daily first void urine and weekly blood samples and questionnaires during BCT. Luteinizing hormone (LH), follicle stimulating hormone (FSH), and metabolites of estradiol (E1c) and progesterone (Pdg) were measured by chemiluminescent assays (Siemens Centaur XP) and adjusted for urinary creatinine (cr). We used independent-samples t-tests to compare maximum values of LH, FSH, E1c, and Pdg between women who did and did not ovulate during BCT. RESULTS: Trainees were young (20.9 ± 4.3 yrs), normal weight (23.7 ± 2.9 kg/m2) women. Most trainees (75%) reported regular menstrual cycles before starting BCT. During BCT, 36 (77%) trainees reported at least one menstrual period, and 41 (87%) reported changes to either menstrual cycle symptoms, length, or frequency. Only three trainees had an ovulatory cycle during BCT. Thus, 94% of women became anovulatory. Mean peak hormone concentrations were higher in ovulatory (O) compared to anovulatory (AO) trainees: Pdg, O 3.2 ± 1.5 vs. AO 1.4 ± 1.4 μg/mg cr (p = 0.0009); LH, O 32.6 ± 5.9 vs. AO 17.6 ± 12.7 mIU/mg cr (p = 0.01); and E1c, O 49.4 ± 12.0 vs. AO 21.7 ± 15.4 ng/mg cr (p = 0.02). FSH was not different between O 44.2 ± 3.5 and AO 34.9 ± 13.1 mIU/mg cr (p = 0.07). CONCLUSIONS: Our findings reveal that HPO axis suppression with anovulation is very common during BCT and occurs among menstruating women.