Your body is brimming with all kinds of hormones, which are chemical messengers that trigger an unfathomable number of different biological processes. One hormone in particular, testosterone, plays an important role in libido--that is, the desire to have sex. If a man's testosterone levels are low, he may lack interest in sex and be unable to have an erection.
If you see a doctor about erection problems, he or she may test your levels of testosterone and other hormones. If your tank is low, hormone-replacement therapy may help you overcome erectile dysfunction.