By Neil Goodman, MD, FACE

A 60-year-old man came to my office because of loss of interest in sex, fewer spontaneous erections than normal, symptoms of depression, and a general lack of strength and pep. He had read a magazine article that said all of this might be caused by low testosterone [teh-STAH-steh-rone] and wondered whether taking testosterone supplements might help.

Loss of sexual desire (or libido) is different from the ability to have and keep an erection for successful sex. Many men have normal sexual interest but have erectile dysfunction. As men age, arousal can decline, which is often related to medical problems, such as heart disease, diabetes, mood disorders, alcohol use, and a decline in testosterone production. Even if testosterone levels are normal, erectile dysfunction can have many causes, including some medications. Testosterone therapy can improve erections in men with low testosterone.

Testosterone levels peak in early adulthood and gradually lessen with age. Because testosterone stimulates libido, muscle mass, red blood cell production, and bone strength, many people think that testosterone supplements are a great anti-aging therapy.

Men with low testosterone can have less motivation or self-confidence, feelings of sadness or depression, or trouble concentrating or remembering things. Yet, the health benefits of testosterone therapy for declining testosterone levels that come with aging aren’t proven.

The only way I could decide if the symptoms my patient had were caused by low testosterone was to measure his blood level of testosterone. Sounds simple, but it is hard to accurately measure testosterone in the blood. Labs that measure testosterone often produce different results from the same blood sample. Therefore, it is hard to have one good normal reference range for testosterone among labs. So, how can we know what is a low testosterone level? The Centers for Disease Control is currently working on creating a standard range for all labs to follow.

In the meantime, endocrinologists [en-doh-cri-NA-lojists], who check and treat hormone problems, are best for figuring out whether low testosterone is clearly the cause of the symptoms. If a man has a low testosterone level, it is most important to understand why the testes are not producing enough testosterone. This condition is called hypogonadism [hie-po-GO-nad-is-m], and can be caused by disorders of the brain, pituitary [pih-TOO-ih-tare-ree] gland, or testes. Chronic illnesses such as heart disease, diabetes, and obesity can cause less testosterone to be produced. Insomnia, caused by sleep apnea, can also cause less testosterone to be produced. Testosterone goes back to normal once the sleep apnea is treated.

Once a low testosterone level has been diagnosed, either the condition that caused it can be treated, or testosterone can be prescribed to bring levels back to normal. Testosterone can either be injected into the muscle, usually every two weeks, or applied to the skin, which is more convenient. Most popular are gels, which are applied daily.

After testosterone therapy is started, the patient must be checked to ensure that the symptoms are properly treated and that side effects aren’t a problem. Potential side effects include enlarging of the prostate gland, which can block the flow of urine and cause the person to have trouble urinating (reduced stream and frequent need to go), especially at night. It is not clear if testosterone therapy can cause prostate cancer, but it may possibly stimulate cancer growth. These and other risks must be regularly evaluated by the patient’s doctor. In older men, the potential benefits are less certain and the potential risks are greater. There is no evidence that otherwise healthy older men with normal testosterone levels would get any benefit from taking testosterone.

Dr. Neil Goodman is board certified in endocrinology, diabetes and metabolism. His private practice specializes in reproductive medicine and he is a Professor of Medicine on the voluntary teaching faculty of the University of Miami Miller School of Medicine. Dr. Goodman currently serves as Chairman of the Reproductive Medicine Committee of the American Association of Clinical Endocrinologists. He is an internationally recognized expert in disorders of reproductive hormones.