“Low T” has become a staple on TV commercials. Like “ED” for erectile dysfunction, low T is a code. It signifies declining testosterone levels, a natural aspect of the aging process.

The ads make it seem as if low T is a serious disease that requires drug treatment. They list common symptoms: fatigue or lack of energy, depression, moodiness, weight gain, reduced muscle strength and diminished interest in sex or ability to perform sexually. Some imply that taking testosterone will help men bulk up their muscles, shed their belly fat and boost their sex drive.

Several of the popular commercials feature relatively young men and gorgeous women. The male actors are presented as suffering from low T, although reduced testosterone production is far more common among older men.

Certainly men troubled by such symptoms should check in with their doctors. Erectile dysfunction can signal health problems from heart disease to diabetes that should be addressed. And although low testosterone levels may be linked to depression, depressed mood alone can zap sex drive and energy. That’s why no man should accept a prescription for testosterone without a test to determine if his testosterone level is actually low.

Even if testosterone levels are reduced, that does not necessarily mean that hormone replacement is called for. Serious concerns have been raised about the potential risks of added testosterone. Men with enlarged prostate glands may find their urinary symptoms become worse. More troublesome, however, is an increased risk for heart attacks.

Testosterone is known to increase production of red blood cells and to make the platelets stickier, so they are more likely to form a clot. Men with high testosterone also tend to have low levels of beneficial HDL cholesterol.

Two recent studies analyzed heart attacks in large groups of men. Researchers at the Department of Veterans Affairs reviewed the records of low-testosterone patients who had received cardiac catheterization. Those who got a prescription for testosterone after their cardiac cath were more likely to die or be hospitalized for a heart attack or stroke in the next three years (Journal of the American Medical Association, Nov. 6, 2013).

An even larger study looked at the records of more than 55,000 men who were prescribed testosterone. Their rate of nonfatal heart attacks in the year prior to the prescription was compared with that for the year after getting the prescription (PLOS One, Jan. 29, 2014). Men over 65 were twice as likely to have a heart attack while taking testosterone. For comparison, the researchers also compared pre- and post-prescription heart attacks for men taking an ED drug such as Viagra or Cialis. This rate was only slightly elevated (15 percent) in men over 65.

This is not to say that a prescription to correct low T is always inappropriate. Really low testosterone can contribute to infertility, osteoporosis and reduced cognitive function.

A prescription for testosterone is not a risk-free way to become lean and sexy, however. Exercise and a healthy diet are cornerstones for good health. The only safe way to build strong muscles is to use them.