Influence of physical exercise on sex-hormone metabolism.

We have studied the effects of short-term exercise on the degradation rate of estradiol (E2) measured as the metabolic clearance rate (MCRE2). Six young women (mean age 20.7 yr) volunteered for this study in which we investigated the influence of a submaximal bicycle ergometer load on the MCRE2. All measurements were done in the morning of the 7th to 10th day of the menstrual cycle. [3H]estradiol 17 beta ([3H]E2) was administered intravenously at a constant rate by an infusion pump. During the exercise period on the bicycle ergometer (70% VO2max, 10 min) and the recovery period (25% VO2max, 30 min), several blood samples were taken in which the [3H]E2 concentration was estimated. The results showed a strong decrease in the MCRE2 (range 18-67%) at the end of the work load for all the volunteers. At the end of the recovery period, the MCR was still lower than the basal value (range 30-50%). The possible mechanisms and relevance of these exercise-induced MCR changes of estradiol are discussed.