Low testosterone often exists with other medical conditions:

Low testosterone often exists with other medical conditions:

• Depression: In a study of almost 4,000 men older than 70, those with the lowest testosterone levels were more than twice as likely to be depressed. This link remained even after allowing for age, general health, obesity, and other variables.
• Erectile dysfunction (ED): Problems with erections are one of the most common symptoms of low testosterone. Most ED is caused by atherosclerosis. Men with risk factors for atherosclerosis -- diabetes, metabolic syndrome, or obesity -- often have low testosterone, too.
• High blood pressure: The effects of testosterone on blood pressure are many and complex. Men with high blood pressure may be almost twice as likely to have low testosterone as men with normal blood pressure. On the other hand, too much testosterone can increase blood pressure. Testosterone acts in multiple ways on blood vessels, so this may account for the varying effects.

Obesity and Low Testosterone

Obesity and low testosterone are tightly linked. Obese men are more likely to have low testosterone. Men with very low testosterone are also more likely to become obese.

Fat cells metabolize testosterone to estrogen, lowering testosterone levels. Also, obesity reduces levels of sex hormone binding globulin (SHBG), a protein that carries testosterone in the blood. Less SHBG means less testosterone.

Losing weight through exercise can increase testosterone levels. Testosterone supplements in men with low testosterone can also reduce obesity slightly.

Metabolic Syndrome and Low Testosterone

Metabolic syndrome is the name for a condition that includes the presence of abnormal cholesterol levels, high blood pressure, waistline obesity, and high blood sugar. Metabolic syndrome increases the risk for heart attacks and strokes.

Studies show that men with low testosterone are more likely to develop metabolic syndrome. In short-term studies, testosterone replacement improved blood sugar levels and obesity in men with low testosterone. The long-range benefits and risks are still unknown.