In briefA college wrestler's weight, body brief fat, and hormone levels were measured during 2 years of competition. Marked weight loss during the initial season was associated with lower serum levels of testosterone and several other hormones, as well as a decrease in reported sexual activity. All values returned to normal after the season. The following year, with less weight loss, the wrestler had only a transient decrease in testosterone and prolactin and reported no decline in sexual activity. Body fat greater than 5% seemed essential to maintaining normal endocrine function.