Simply getting older is the number one cause of low testosterone. That’s because your testosterone level goes down naturally as you age. If you're older than age 60, you have a one in five chance of a low T level. But age isn't the only cause of low testosterone. Diabetes and obesity both have a link to low T. If you have either one, you have about a 50% chance of having low T. If you have low T at a younger age, your health care provider might look for other causes. Drugs, injuries, and lack of sleep can all be to blame. So can cancer, or even cancer treatments. Here are five more medical conditions that can cause low T. 1. Pituitary Tumors Your pituitary gland lies underneath your brain. This gland makes chemical messengers that control how much testosterone your testicles make. A pituitary tumor is rarely cancerous. If you have a large pituitary tumor, you may have headaches or changes in eyesight. But, a pituitary tumor can also interfere with how your body regulates testosterone. This can cause low T. This can lead to a loss of sexual desire, a low sperm count, and breast enlargement. 2. Alcoholism Lower testosterone is one result of alcohol abuse and alcoholism. Alcoholism can disrupt the messages sent from your brain to your testicles, directing testosterone production. Drinking too much alcohol can also directly block your testicles from making testosterone. Long-term alcohol abuse leads to cirrhosis, a serious scarring of your liver. Cirrhosis also causes low T. 3. HIV/AIDS HIV may have a direct effect on your brain. HIV interferes with the chemical messengers needed for making testosterone. Up to 20% of men who are treated for HIV have low T. HIV-related liver damage, drug abuse, or weight loss can also contribute to low T. If you have symptoms like fatigue, depression, and trouble concentrating, testosterone treatment may help. 4. Klinefelter Syndrome This genetic condition affects up to one in 500 men. If you have it, you're born with an extra sex chromosome. Symptoms usually begin around the time of puberty. Boys with Klinefelter make only about half as much testosterone as they should. Symptoms include breast enlargement, poor muscle development, and social problems. Your risk for Klinefelter is higher if your mother was older than 35 when she gave birth to you. Treatment with testosterone is helpful. 5. Hemochromatosis If you have this inherited condition, your body absorbs too much iron from your diet. The extra iron can build up in your organs, including your testicles. Over time, the iron can damage your testicles and cause low T. Symptoms may not start until you reach middle age. They can include fatigue, loss of sex drive, weight loss, and pains in your belly or joints. Treatment for hemochromatosis involves having blood taken from your arm on a regular basis. Key Takeaways Low T is more common as you age, but there are other causes. Common conditions like obesity, diabetes, and HIV have been linked to low T. Alcoholism can cause low T directly and by damaging your liver. A noncancerous tumor of your pituitary gland can cause low T. Klinefelter syndrome and hemochromatosis are two causes of low T you're born with.