Each sperm produced by the testes takes about seventy-two days to mature and its maturity is overseen by a complex interaction of hormones. The scrotum has a built-in thermostat that keeps the testes and sperm at the correct temperature. It may be surprising that the testes should lie in such a vulnerable place outside the body, but it is too hot for them inside. Spermatogenesis requires a temperature that is three to five degrees Fahrenheit below body temperature. If it becomes too cool on the outside, the cremaster muscle will contract to bring the testes closer the body for warmth.
Are your hormones in tune? Mounting evidence suggests that exposure to light at night -- whether you're asleep or awake -- might play a crucial role in cancer, diabetes, and obesity. The World Health Organization classified "circadian disruption" as probably carcinogenic, and light at night is considered by some to be an endocrine disruptor that may affect melatonin, cortisol, ghrelin, leptin, and testosterone. "Most people think, and the drug companies want you to think, that waking up at night is bad for you," says Richard Stevens, ., a cancer epidemiologist at the University of Connecticut health center. But that's not the case, he says -- it's exposure to light at night that's the problem. "If you wake up at night, as most of us do, that is a period of quiet wakefulness -- stay in bed, in the dark, and enjoy it," Stevens suggests.