Testosterone is a hormone made by the testicles. It is important for a man's sex drive and physical appearance.

Certain health conditions, medicines, or injury can lead to low testosterone (low-T). Testosterone level also naturally drops with age. Low testosterone can affect sex drive, mood, and changes in muscle and fat.

In men, hormone levels change gradually, if at all. Research has shown that a third of men over age 45 will have low testosterone. In general, testosterone levels vary greatly among men, and some men never experience “male menopause.”

Testosterone helps regulate so much of the body’s chemistry that when its levels fall, many organ systems are affected. Low testosterone is linked to bone loss and possibly heart disease.

Beginning around age 30 to 40, testosterone levels may start to slowly decrease. This occurs naturally.

Other causes of low testosterone include:

  • Medicine side effects, such as from chemotherapy
  • Testicle injury or cancer
  • Problems with glands in the brain (hypothalamus and pituitary) that control hormone production
  • Low thyroid function
  • Too much body fat (obesity)
  • Other disorders, chronic diseases, medical treatments, or infection

Symptoms of Low Testosterone

Men with low testosterone may gain weight around the abdomen and lose muscle tone in their arms and legs. Many men feel fatigued and even depressed. Some don’t sleep well and have trouble concentrating. Some symptoms may be a normal part of aging. For example, it is normal to feel less interested in sex as you get older. But, it is not usually normal to have no interest in sex.

Symptoms may also be caused by other conditions, such as high blood pressure. If any of these symptoms are bothering you, talk with your health care provider.

Low Testosterone Treatment

Testosterone is not given to men who want to have children because it can interfere with sperm production and cause infertility. Other than the risk of infertility, the risks of hormone treatment are minimal. Doctors monitor red blood cell count, to make sure it doesn’t get too high. The hormone may cause skin irritation or breast tenderness. Some studies have linked it to prostate cancer, but so far there’s no proof. Any man considering testosterone treatment should be screened for prostate cancer and hormone therapy should not be used in men diagnosed with untreated prostate cancer.

Testosterone is often prescribed as a cream that’s absorbed through the skin. Patients rub it on their arm, shoulder or abdomen once a day. Injections are also available and are given every two to three weeks. There’s no oral form of the drug approved in the U.S.

With testosterone treatment, most patients report immediate improvement in the way they feel. Their sex drive returns. They feel energetic again, and their mood improves.

It is important to remember that not all men develop low testosterone. There may be other explanations for low energy, depression and the growing paunch. But for men who do suffer from low testosterone there’s plenty of truth in the phrase “male menopause.”