Endurance exercise training does have significant effects on the major male reproductive hormone, testosterone, and the hypothalamic-pituitary-axis that regulates testicular function. A growing body of evidence suggests that testosterone is chronically lowered in endurance exercise-trained men, and we have referred to this condition as exercise hypogonadism. Although the mechanism of this testosterone lowering is currently unclear, it may be related to a dysfunction or a readjustment in the hypothala-mic-pituitary-testicular regulatory axis brought about by years of endurance training. Currently, the time course of these changes, including their reversibility, remains unresolved and is in need of further scientific investigation (137). The lowered testosterone levels of the exercise-hypogonadal male could potentially disrupt anabolic or androgenic testosterone-dependent processes. Conversely, the alterations in testosterone levels brought about by endurance training could have cardiovascular protective effects and may, thus, be beneficial to these men.
Similar reproductive hormonal profiles exist in exercise-hypogonadal men and in men who are undergoing overtraining who develop the overtraining syndrome. However, the hormonal changes with the overtraining syndrome are transient and reflect the stress of excessive physical training. An increase in the rest and recovery portions of training regimens eliminates any hormonal abnormalities in overtraining men but not in exercise-hypogonadal men.
Some athletes are using anabolic-androgenic steroid agents to induce muscular growth, development, and strength gains. Current evidence suggests that they are effective in producing the outcomes that athletes desire. Unfortunately, athletes are ignorant of, or are willing to ignore, the serious medical side effects and health consequences associated with using these agents. Unfortunately, their use has been a persistent occurrence and problem in sports for the last 50 yr.
Although there is a large volume of literature concerning the reproductive endocrine dysfunction in exercising women, the number of studies in males is relatively small. Thus, many questions regarding the male reproductive adaptive process to exercise training remain unanswered. Consequently, this area of exercise endocrinology is in need of continued study and investigation.
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