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  • Writer's pictureAlan Frischer, MD, MPH


My male patients often come to see me with concerns about a low libido (sex drive) and erectile problems. There are a number of possible causes (including stress, poor sleep, alcohol or drug problems, diabetes, smoking, thyroid function, and hypertension), but what patients most often blame is low testosterone. The American Urology Association states that roughly 40% of men over the age of 45 are affected by low testosterone. Let’s look at this critical hormone.

Everybody produces testosterone, regardless of gender. It is made in the testes in men, in the ovaries in women, and in the adrenal glands in both men and women. In the interests of keeping my remarks (somewhat) brief, today I will focus on men.

Starting at the fetal stage, testosterone guides the development of the male external and internal organs. During puberty, testosterone is responsible for growth spurts, deepening of the voice, and growth of hair in the pubic region, face, and underarms. Testosterone is also associated with aggression and sex drive, and, of course, it enables men to produce sperm for reproduction.

What does low testosterone in adult men look like? Symptoms include reduced body and facial hair; loss of muscle mass and higher levels of stomach fat; low libido, impotence, small testicles, reduced sperm count and infertility; increased breast size; hot flashes; irritability, poor concentration and depression; brittle bones; and insulin resistance, which can lead to diabetes.

Common causes of low testosterone include chronic diseases like diabetes; damage to the testes from physical trauma, alcoholism, or viral diseases; genetic diseases such as Klinefelter, Kallman, or Prader-Willi syndromes; hypothalamic or pituitary diseases or tumors; and testicular failure.

What does abnormally high testosterone look like? Symptoms includes a low sperm count; shrinking of the testicles and impotence; heart muscle damage and increased risk of heart attack; prostate enlargement with difficulty urinating; liver disease; acne; fluid retention with swelling of the legs and feet; weight gain; high blood pressure and cholesterol; insomnia; headaches; increased muscle mass; increased red blood cell levels, increased risk of blood clots; stunted growth in adolescents; uncharacteristically aggressive behavior (although this is not well studied); and mood swings, euphoria, irritability, impaired judgment, and delusions.

Causes of excess testosterone include congenital adrenal hyperplasia, taking anabolic steroids, or tumors of the testicles or adrenal glands. Some medications can also increase testosterone levels, including anticonvulsants, barbiturates, and estrogen therapy.

Testosterone levels in men typically peak at around age 30, and then gradually decrease from that age forward. So, lower testosterone levels are more common among older men, and this helps to explain other age-related changes, such as loss of muscle mass.

If treatment for low testosterone is necessary, choices include topical gels, patches, injectable testosterone, and implantable testosterone. However, side effects can include acne, breast tenderness or enlargement, elevated red blood cells, infertility, small testicles, swelling of the lower extremities, and emotional effects such as anger, anxiety, and aggression. As you would expect, these treatments require careful monitoring by a physician.

There is no evidence that testosterone replacement therapy increases the risk of prostate cancer. However, since reducing the testosterone level is one form of treating prostate cancer, testosterone therapy is not recommended for men with known or previously treated prostate cancer.

Checking testosterone levels is easy; it’s a simple blood test. The difficult part is interpreting the result. The optimal amount of testosterone is far from clear. Levels vary over the course of the day, and a single low level may be meaningless if there are no symptoms, especially if it is normal at another time. Research continues to determine when to measure testosterone, how best to respond to the results, and when it makes sense to accept the risks of treatment. I urge you to speak with your doctor if you believe that you have a problem with testosterone.

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