context: Researchers are unlocking the mysteries of how low testosterone is related to men's overall health. Along the way, they're uncovering connections between low testosterone and other health conditions. Diabetes, metabolic syndrome, and obesity have all been linked to testosterone deficiency. Low testosterone isn't known to cause these health problems, and replacing testosterone isn't the cure. Still, the associations between low testosterone and other medical conditions are interesting and worth a look. In recent years, researchers have noticed general links between low testosterone and other medical conditions. One study showed that in 2,100 men over age 45, the odds of having low testosterone were: 2.4 times higher for obese men 2.1 times higher for men with diabetes 1.8 times higher for men with high blood pressure Experts don't suggest that low testosterone causes these conditions. In fact, it might be the other way around. That is, men with medical problems or who are in poor general health might then develop low testosterone. Research into the relationship between low testosterone and several other health conditions is ongoing. A link between diabetes and low testosterone is well established. Men with diabetes are more likely to have low testosterone. And men with low testosterone are more likely to later develop diabetes. Testosterone helps the body's tissues take up more blood sugar in response to insulin. Men with low testosterone more often have insulin resistance: they need to produce more insulin to keep blood sugar normal. As many as half of men with diabetes have low testosterone, when randomly tested. Scientists aren't sure whether diabetes causes low testosterone, or the other way around. 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 free testosterone. Losing weight through exercise can increase testosterone levels. 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. However, testosterone therapy increases the risk of heart disease, so it is not used to treat metabolic syndrome. Testosterone has mixed effects on the arteries. Many experts believe testosterone contributes to the higher rates of heart disease and high blood pressure that tend to affect men at younger ages. By this reasoning, high testosterone might be bad for the heart. But testosterone deficiency is connected to insulin resistance, obesity, and diabetes. Each of these problems increases cardiovascular risk. Men with diabetes and low testosterone also have higher rates of atherosclerosis, or hardening of the arteries. A certain amount of testosterone may be necessary for healthy arteries because it's converted into estrogen, which protects arteries from damage. As yet, no studies show that testosterone replacement protects the heart or prevents heart attacks. 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 and libido (sexual desire) are common symptoms of low testosterone. While most ED in older men is caused by atherosclerosis, an evaluation for low testosterone may be warranted. The question that remains is, does low testosterone cause or worsen medical problems like diabetes? Or are people who develop diabetes, or other health problems, simply more likely to also have low testosterone? Studies to answer these questions are under way, but it will be years before we know the results. In the meantime, remember that testosterone replacement hasn't been conclusively shown to improve any health condition other than testosterone deficiency and its symptoms. For men with low testosterone levels as measured by a blood test who also have symptoms of low testosterone, the decision to take testosterone replacement is one to make with your doctor.