As men age, their bodies produce less of the hormone testosterone. This is a natural process—the decline starts around age 30—and ordinarily, enough testosterone has been produced before then to maintain appropriate levels for a long time. Sometime, however, the level of the hormone falls below a critical point, which can cause a variety of issues. This is more likely to happen in men who are obese or who have one of several medical condition often associate with obesity, such as diabetes or heart disease.
Testosterone is thought of as a sex hormone, but that provides only a very narrow picture of its functions in the body. For one thing, it is found in both men and women. In fact, the female hormone estrogen is made from testosterone, meaning it is essential for women as well as men. However, most of its effects are largely found in men, and lack of testosterone is a bigger problem for men than for women.
Often the most noticeable effects of low testosterone are sexual: men who have had a decline in testosterone levels have a reduced sex drive, lessened sexual responsiveness, and difficulties with physical arousal. On the non-sexual side, low hormone levels can mean less energy overall, even after a day that isn’t particularly taxing. Often people with low testosterone will develop clinical depression, or a pervasive low mood that falls short of depression but interferes in tasks, relationships, and enjoyment of life in much the same way. Testosterone levels also affect bone density, meaning a drop can leave someone prone to osteoporosis and in danger of fractures.
Some men have even more to worry about. Prostate cancer, in many cases, is, if not harmless not a cause for concern. Many men are posthumously found to have had prostate cancer that showed no symptoms and barely affected their apparent health. Even when it is diagnosed during the patient’s life, doctors may decide that a mild, slow-moving, low-risk prostate cancer poses less of a threat than treatments would. However, researchers have found that in these slow-moving cases, a sudden drop in testosterone can indicate that the cancer is worse than previously recognized.