Hormone Profiles After Planned Low Energy Availability Exposure in Naturally Menstruating and Hormonal Contraceptive...

This observational study investigated the potential influence of hormonal contraceptive (HC) use on selected hormonal biomarkers (estradiol, total testosterone, IGF-1, cortisol, triiodothyronine, and leptin) that respond to diet and physical training-induced low energy availability (LEA). Thirty-six female physique athletes-combined HC users (n = 11), low-dose progestin-only HC users (n = 11), and naturally menstruating females (n = 14)-prepared for a physique competition. All participants voluntarily restricted energy intake while simultaneously participating in resistance training to maintain lean mass and aerobic training to increase energy expenditure. Measurements were completed over approximately 46 weeks as follows: before commencing the pre-competition period, including dietary restriction and physical training (pre); after ∼23 weeks of dietary restriction and physical training (post); and after ∼23 weeks of recovery (recovery). Hormones were analyzed from fasting blood samples, whereas body mass, fat mass, fat-free mass, and body fat percentage were measured using bioimpedance. Our main findings established that after ∼23 weeks of LEA, concentrations of estradiol and total testosterone remained stable in the combined HC users but decreased significantly in progestin-only HC users and naturally menstruating females. Serum IGF-1, triiodothyronine, and leptin decreased comparably from pre to post in all groups, whereas serum cortisol concentrations remained statistically unchanged throughout the investigation. These results indicate that the exogenous hormones in combined HCs users may maintain already suppressed hypothalamic-pituitary-ovarian axis function in the presence of LEA, whereas LEA-induced changes in IGF-1, triiodothyronine, and leptin may be comparable in combined and progestin-only HC users and naturally menstruating females. TRIAL REGISTRATION: The second study was registered at ClinicalTrials.gov ID: NCT04392752.