Sleep loss lowers testosterone.....

I'm off to bed

Cutting back on sleep drastically reduces a healthy young man's testosterone levels, according to a study published in the June 1 issue of the Journal of the American Medical Association (JAMA).

Eve Van Cauter, PhD, professor in medicine and director of the study, found that men who slept less than five hours a night for one week in a laboratory had significantly lower levels of testosterone than when they had a full night's sleep. Low testosterone has a host of negative consequences for young men, and not just in sexual behaviour and reproduction. It is critical in building strength and muscle mass, and bone density.

More here, but I can't get the full thing.