Overtraining and testosterone

This is interesting and mildly disturbing:

Male functional hypogonadotropic hypogonadism (MFHH): A distinct clinical entity?

Males presenting with high athletic stress or weight loss, coupled with low testosterone, may signal the rise of a new disorder -- functional hypogonadotrophic hypogonadism.
Just as women whose bodies are under stress from excessive exercise, weight loss, or psychological stress can experience hypothalamic amenorrhea, a seven-patient series suggests that a similar phenomenon may exist among men undergoing similar kinds of stress, Andrew Dwyer, MD, of Massachusetts General Hospital, said during a poster session here at the annual meeting of the Endocrine Society.

Basically in some people training too much leads to lowered levels of testosterone.

Dwyer noted that after the patients had been tested, one of them sustained a heel injury and had to stop training for a while. "He gained six pounds, and we measured his testosterone level, and serially, it stayed normal," he noted. "So with just enough removal of stress...he was able to swing back into normal testosterone production."

Another patient who decreased his training upon the researchers' recommendation was also retested and his testosterone level was up into the low end of the normal range, said Dwyer.