What role does testosterone play?
Just how important is testosterone for preventing heart disease in men?
Just 20 years ago, this question wouldn't have even been asked. Traditional teaching was that, because men develop heart disease earlier than females (by 10 years), testosterone must therefore cause heart disease.
But observations accumulated since then have turned this misconception topsy-turvy:
Not only does testosterone not cause heart disease, it may in fact be protective.
Testosterone levels peak in a male's 20s during his reproductive prime. That's also the period of a man's greatest physical capacity, muscle mass, physical energy, libido, and stamina. Starting at age 30, testosterone levels diminish. By the time a man reaches his 70s, testosterone has dropped to low, sometimes unmeasurable, levels.
Coincidentally (?), a male's increasing risk for heart disease with aging parallels the decline in testosterone. Indeed, several studies have connected lower testosterone blood levels with greater likelihood of heart attack. An 11,000-participant European study (EPIC Norfolk), for instance, showed that the men with the highest testosterone levels (natural, without supplementation) had 40% fewer deaths from heart attack and cancer. An NIH-sponsored study (The Aging in the Chianti Area Study) showed a 48% higher mortality rate (cardiovascular and cancer) in men with low testosterone. In another study, a marked deficiency of testosterone ("hypogonadism") was found in 25% of men with coronary disease (history of heart attack or major heart procedures).
Several other studies in the U.S. and elsewhere have confirmed similar observations: The lower the testosterone, the greater the likelihood of heart attack.
How might testosterone be related to heart disease risk? Let's look at some of the observations that have been made:
- Testosterone increases the production of the natural arterial dilator, nitric oxide, and suppresses growth of smooth muscle cells in arteries (a constituent of plaque). Lack of testosterone does the opposite.
- Improvement in abnormal resistance to insulin-This is the essential phenomena behind pre-diabetes and metabolic syndrome. Men with pre-diabetes and diabetes have low testosterone much more frequently than men without these conditions.
- A dramatic reduction in inflammatory proteinsHeart disease is, to a large degree, a consequence of inflammatory responses. Lack of testosterone permits an explosion in inflammatory responses.
Low testosterone levels also lead to loss of muscle mass, increased abdominal fat, and reduced libido. Mood disruptions develop, with deeper swings into blue, depressed feelings, struggles with feeling beaten and overwhelmed, and fatigue. Reduced concentration, irritability, passivity, loss of interest in activities, and even hypochondria can also result, changes that often become insidiously perceptible after a man passes beyond his mid-40's. Some call this time the "male menopause" or "andropause." Though not as visible as a woman's transition to menopause, the changes are indeed distinct. Since there's no external cue like cessation of a woman's menstrual period, most men simply dismiss the changes as "getting old."
Testosterone replacement can be a helpful way to reverse many of the phenomena of reduced testosterone: gain vigor, increase muscle mass, and partially restore lost libido.
While low testosterone levels have been firmly and inarguably associated with increased risk for heart disease and heart attack, what we lack is a large trial involving a substantial number of men (thousands) that shows that testosterone vs. placebo yields any genuine heart attack-reducing benefits.
My prediction is that testosterone replacement will indeed reduce heart disease risk by a significant marginnot eliminate risk, but just be an important addition to a broader program of prevention. Until such a large clinical trial is performed, however, the benefits of testosterone remain somewhat uncertain.
Nonetheless, testosterone status is something worthy of conversation between every male and his doctor.
Coming next: Part II: Testosterone: A practical guide to replacement