DEAR DOCTOR K: I’m a man in my early 50s. Lately, my sex drive isn’t what it used to be. Plus, I’m irritable and depressed. Could I have low testosterone?
DEAR READER: Yes, you could, but that’s not the only possible explanation of your symptoms. There are some rare diseases that can cause very low blood levels of testosterone and a host of symptoms. I won’t be talking about those in this column. Instead, I’m talking about a more common condition.
Testosterone is the major sex hormone in men. As men get older, testosterone production falls. If it falls low enough, it can cause some of the symptoms you described.
Testosterone plays a number of important roles, even after puberty. It affects muscle size and strength, bone growth and strength, sex drive (libido), sperm production and mood.
A cascade of chemical signals leads to the production of testosterone. One part of the brain (the hypothalamus) sends a signal to another part (the pituitary gland). The pituitary gland then relays signals to the testes to produce testosterone.
As blood levels of testosterone rise, a “feedback loop” kicks in: When levels rise high enough, the brain temporarily shuts down the signals that lead to more testosterone. When blood levels fall, the brain turns the signals back on.
During teenage years and early in adult life, this signaling system works fine. However, for reasons we don’t understand, as men get older the pituitary gland sends fewer signals and the testes produce less testosterone.
It’s similar to what happens during menopause in women, when the brain stops signaling the ovaries to make female hormones. In fact, some experts call this reduction in testosterone, and the symptoms it can cause, “andropause.”
The main symptoms of andropause include:
• low sex drive;
• low energy;
• erectile dysfunction (difficulty having an erection);
• decreased muscle mass.
There are many other causes of these symptoms. For example, men start losing muscle mass as they get older, even if their testosterone levels are normal. And depression is a common cause of low sex drive, low energy and erectile dysfunction. In fact, most men with these symptoms have causes other than low testosterone. However, if a man with these symptoms has low blood levels of testosterone, and if these symptoms improve when a man is given testosterone replacement, he is probably experiencing andropause. Testosterone replacement can be given through testosterone injections or a patch.
Testosterone treatment has some potential side effects. Most doctors are reluctant to prescribe testosterone for a man who has prostate cancer, or who has several close relatives with prostate cancer. The concern is that the testosterone hormone will encourage cancer cells to grow. The evidence in support of this is, in my opinion, not clear-cut, but it’s a real concern.
On my website (AskDoctorK.com), I’ve included some questions and answers about testosterone symptoms written by my colleague Dr. Abraham Morgentaler in his book “Testosterone for Life.”
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.