Relationship of resting prolactin and testosterone in males during intensive training.

Recently, findings of lowered serum testosterone levels and other hypogonadal symptoms have been reported in endurance trained males",2. The mechanisms of these changes have been proposed to be similar to those put forth for females experiencing athletic amenorrhoea, a disruption of the hypothalamic-pituitary-gonadal axis. In preliminary findings, we have found a relationship between changes in resting serum prolactin and testosterone levels in males undergoing exercise training. Nine healthy, athletic males were placed on an eight week intensive training programme (5 day/week, > 90 minutes/day). The training involved cycle ergometry, and contained a combination of continuous (70 per cent maximal aerobic power) and interval (80-150 per cent maximal aerobic power) based training. Every two weeks the maximal aerobic power of the subjects was re-evaluated and new training loads prescribed. This training protocol was selected to mimic what competitive athletes typically perform. Resting (10 hour post-prandial) blood samples were collected every Monday morning, after two days rest, at two week intervals throughout the study. Table 1 shows the hormonal changes (mean±SEM) observed. Significant changes (P < 0.05; ANOVA) from pre-training levels are denoted with an asterisk. The four to six week testosterone levels were significantly reduced while prolactin levels were significantly elevated during this time. Correlation analysis (Pearson-product) of the changes observed in the two hormones resulted in an r = -0.934 (P < 0.01). These