What Is Testosterone? Testosterone may be the most notorious of hormones. It conjures up thoughts of muscles and masculinity. In fact, testosterone does fuel sex drive and muscle mass, but it also regulates mood and bone strength. When a man's level falls below normal, a doctor may prescribe shots, gels, or patches. But there is some debate over who needs treatment. Aging and Testosterone Levels A slow drop in testosterone is a normal part of aging, sometimes called "andropause" or "male menopause." For many men, this doesn't cause any significant problems or symptoms. Others may notice hot flashes, irritable moods, or less interest in sex. Low Testosterone and the Body Low testosterone can cause visible changes in some men: Thinner muscles Loss of body hair Smaller, softer testicles Larger breasts Low Testosterone Affects Bones You may think osteoporosis, or brittle bone disease, is a woman's disease, but it can affect men as well. Low testosterone is a common cause. As testosterone levels fall, the bones may get thinner, weaker, and more likely to break. Low Testosterone and Sex A drop in testosterone doesn't always interfere with sex, but it can make it more difficult for your brain and body to get aroused. Some men may notice a drop in libido, while others may lose interest in sex completely. Low testosterone can also make it tougher to get or keep an erection. Testosterone, Mood, and Thinking Some men have subtle problems like irritability or other mood changes, poor concentration, and less energy. These symptoms can easily be caused by other health problems though, like anemia, depression, sleep troubles, or a chronic illness Low Testosterone and Infertility Testosterone helps a man's body make sperm. When levels of the hormone are low, his sperm "count" can be low, too. Without enough sperm, he may not be able to father a child. What Causes Low Testosterone? Getting older is the most common reason testosterone levels dip. Illnesses are sometimes to blame, including: Type 2 diabetes Liver or kidney disease COPD Pituitary gland problems Testicle injuries Radiation therapy, chemotherapy, and steroid medicines can also affect testosterone levels. Should You Be Tested? Your doctor may suggest a testosterone test if you have: erectile dysfunction Lower sex drive Low sperm count A loss of height, body hair, or muscle size If you have an illness known to lower testosterone, your doctor may want to test your levels of the hormone. Testosterone Replacement Therapy If you need treatment, your doctor may prescribe testosterone to boost your levels. Some studies suggest this can strengthen a man's muscles, protect his bones, and improve his sex drive. But the effects can be quite different from one man to the next. Testosterone Injections Testosterone comes in several forms, including shots, gels, patches, and tablets you place on your gums. Injections are the least expensive option, but they can be painful. You take the shots every 7 to 22 days, as prescribed by your doctor. Your testosterone levels can swing up and down between doses. Testosterone Gels or Patches These are placed directly on your skin. The hormone seeps through the skin, and is slowly released into the blood. Because gels and patches are applied every day, they keep a steady level of testosterone. However, they can cause itching, irritation, and blisters. Women and children should not touch skin treated with a gel or patch. Who Should Not Take Testosterone? Men with these conditions shouldn't take testosterone: Prostate or breast cancer Poorly controlled heart disease Untreated sleep apnea Too many red blood cells Source