To relate endocrine and nutritional correlates of fitness in postpubertal physically active females across the normal weight spectrum to identify markers and how these might serve as associations of exercise-related endocrine disruption.
Cross-sectional study analyzed by repeated-measures analysis of variance for frequent blood sampling.
A general clinical research center.
Twenty-two healthy postpubertal female subjects recruited 2 years or more after menarche.
Main Outcome Measures
Maximum oxygen consumption was determined as an index of fitness and daily caloric intake was calculated from a 3-day food diary. During the follicular phase of the cycle, luteinizing hormone was sampled every 10 minutes during a 24-hour period, while follicle-stimulating hormone and cortisol were sampled hourly.
For every 1-unit increase in maximum oxygen consumption, cortisol concentration increased by 2% (P = .005; 95% confidence interval, 1%-3%). However, there was no association between mean gonadotropin concentrations and fitness. Hormone concentrations were not significantly associated with body mass index or percentage of body fat. Higher mean caloric intake from a 3-day summary was inversely related to mean luteinizing hormone concentration, which decreased by 5.5% for every 100-kcal increase (P = .03; 95% confidence interval, 1%-10%). With every 1-year increase in age at menarche, follicle-stimulating hormone concentration decreased by 12% (P = .01; 95% confidence interval, 4%-19%) and cortisol concentration increased by 7% (P = .03; 95% confidence interval, 1%-12%).
In active adolescents, increased cortisol concentration may represent an adaptive change to exercise that may precede gonadotropin changes seen with higher levels of fitness.