Impaired gonadotropin responses to gonadotropin-releasing hormone stimulation in endurance-trained women

The effects of endurance running on body composition, menstrual cycles, and gonadotropins were studied in 19 healthy, young, regularly menstruating women. Midfollicular plasma concentrations of unstimulated and gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone and follicle-stimulating hormone were examined at baseline and after each subject’s weekly mileage had increased 30 miles (Δ30) and 50 miles (Δ50) above baseline. Mean±standard error of the mean unstimulated luteinizing hormone and follicle-stimulating hormone did not change significantly. GnRH-stimulated luteinizing hormone was 76.3±22.0μg/min/ml at baseline and declined to 20.2±4.5μg/min/ml at Δ50 (P