Unique Effects of Energy versus Estrogen Deficiency on Components of Bone Strength in Exercising Women

Abstract

Exercising women with menstrual disturbances are at risk for poor bone health due to hypoestrogenism. Energy deficiency often instigates menstrual dysfunction resulting in metabolic adaptations that independently threaten bone. Women experiencing both an energy and estrogen deficiency face an exacerbated risk to bone health. PURPOSE: To describe volumetric bone mineral density (vBMD), bone geometry, and estimated bone strength in exercising women (n=50) grouped by energy status (energy replete (EnR: n=25); energy deficient (EnD: n=25)) and estrogen status (estrogen replete (E2R: n=24); estrogen deficient (E2D: n=26)) resulting in four groups: EnR+E2R (n=12), EnR+E2D (n=13), EnD+E2R (n=12), EnD+E2D (n=13). METHODS: Energy status was defined by the ratio of measured to predicted resting energy expenditure (mREE/pREE). Estrogen status was defined by self-reported menstrual status and confirmed by assessment of urinary metabolites of reproductive hormones over one menstrual cycle or 28 day monitoring period. Peripheral quantitative computed tomography assessed vBMD, bone geometry, and estimated bone strength at the radius and tibia. RESULTS: The groups were similar in age (21 ± 0.4 years), gynecological age (8 ± 0.5 years), height (165.7 ± 0.9 cm), and weight (57.7 ± 1.2 kg). At the proximal tibia, EnD women exhibited significantly lower total vBMD, cortical area, and cortical thickness and greater endosteal circumference than EnR women (p≤0.020). E2D women exhibited significantly lower total and cortical vBMD and bone strength index (BSI) and greater total and trabecular area (p≤0.040) at the distal radius and lower cortical vBMD and thickness (p≤0.019) at the proximal radius compared to E2R women. EnD+E2D women had significantly lower total and trabecular vBMD at the distal tibia and radius and total vBMD and cortical thickness at the proximal tibia compared to EnR+E2D women (p≤0.048). CONCLUSION: Energy versus estrogen status affected bone differently and effects were site-specific. Women with both an energy and estrogen deficiency experienced the most adverse bone adaptations. Treating energy deficiency in exercising women may improve reproductive health, in turn addressing the unique contributions of energy status versus estrogen status to bone health. Supported by US DoD (PR054531).