In men, testosterone levels decline around the age of 30 and by age 80 may be down to 20% of someone in their 20s. Men with low testosterone tend to have less stamina, reduced muscle mass and reduced libido. They can also have cognitive problems as well as depression and anxiety. The thing you really notice in men with low testosterone levels is a lack of initiative—they fit the stay-at-home, couch potato stereotype. They may say things like, “I used to like to work on the car (go on a hike, go dancing, work around the yard, etc.), but I really don’t feel like doing that anymore.”

Low testosterone can lead to more serious health problems. It is linked to obesity (and increased abdominal fat), diabetes and heart disease. In the journal, Circulation (2007;116:2694-2701), a study examined the prospective relationship between endogenous testosterone concentrations and mortality due to all causes, cardiovascular disease, and cancer in a nested case-control study based on 11, 606 men aged 40 to 79 years. The researchers concluded that endogenous testosterone concentrations are inversely related to mortality due to cardiovascular disease and all causes. Low testosterone may be a predictive marker for those at high risk of cardiovascular disease. Other research (Circulation 1999;100:1690-1696) showed  that short-term intracoronary administration of testosterone, at physiological concentrations, induces coronary artery dilatation and increases coronary blood flow in men with established coronary artery disease.

Women can have low testosterone as well. Levels decline between the ages of 20 and 40. An article appearing in  the journal, Clinical Geriatric Medicine (2003;19:605-616) reviews the changes a woman goes through when testosterone levels decrease. When a woman receives estrogen for hormone replacement therapy after menopause, there is an increase in sex hormone-binding globulin. The sex hormone-binding globulin binds to testosterone, further decreasing levels. Low testosterone is linked to a decrease in libido, as well as a decrease in muscle mass, fatigue, irritability, sleep disturbances, poor memory and cognition, headaches, and even depression.