Jan. 15, 2003 -- It's a controversial topic -- should men get testosterone replacement therapy when they hit midlife? A review of research finds that twice as many men with heart disease have low testosterone levels compared with men without heart disease. In fact, low testosterone is linked to a number of risk factors for heart disease.
Around the world, men are three times more likely to have heart disease than women, writes Kevin Channer, PhD, a researcher at Great Britain's Royal Hallamshire Hospital, located in Sheffield. His editorial appears in the current issue of the journal, Heart.
However, the influence of sex hormones on heart disease in men "has been relatively ignored," Channer says
Studying testosterone has been difficult, he writes. Only a small amount is flowing in the bloodstream, and that amount varies by age, body type, and weight -- partly because testosterone can get broken down into estrogen, and partly because the hormone levels decline with age.
Recent studies have shown that men with heart disease have significantly lower concentrations of testosterone in their blood. Also, a condition called hypogonadism -- a glandular disorder that causes low testosterone levels production -- is twice as common in men with heart disease than in the general population, Channer adds.
Men with overly high testosterone levels also have high LDL (the "bad" cholesterol), low HDL (the "good" cholesterol), high triglycerides (also "bad"); they also are more likely to be diabetic and have high blood pressure, he writes.
Studies have shown that increasing doses of testosterone in arteries causes them to dilate, increasing blood flow, and in veins, it improves exercise tolerance and reduces angina in men with heart disease. There is currently no evidence that testosterone replacement in men with hypogonadism increases their rate of prostate cancer -- however, those studies have been small, Channer concedes.
The subject of testosterone replacement therapy has caused much controversy over the past two or three decades, says Joseph Zmuda, PhD, an epidemiologist at the Graduate School of Public Health at University of Pittsburgh. Zmuda commented on the editorial for WebMD.
"Most studies have been inconclusive," he tells WebMD. "However, studies in animals suggest that if male rabbits have too little testosterone, they develop more atherosclerosis [hardening of the arteries] than animals with normal testosterone. And if we replace testosterone, we prevent development of atherosclerosis."
Five long-term epidemiological studies -- tracking large groups of men -- all found absolutely no evidence that there's any relationship between a man's testosterone level and his risk of dying of a heart attack, says Zmuda.
But the issue is much more complicated than that, he adds.
Two recent studies use newer, more precise technology to measure atherosclerosis, and both show that men with lower levels of testosterone had more atherosclerosis. "However, both studies were relatively small, so the findings need to be confirmed," Zmuda says.
"The very issue of giving men hormone replacement therapy is very complicated," he tells WebMD. "Just as with women, we have to be very careful about giving sex hormones to men. It would have to be given to men for a very long period of time, since in men the decline occurs much more gradually. In women, estrogen drops off more abruptly, so there's a more clear-cut time to give it."
"I would be concerned about the long-term risks of prostate cancer," he adds. "There's a lot more works that need to be done in this area."