A direct association between testosterone and heart disease has never been established, but for many years, doctors have suspected that a link exists. The reasoning goes like this: men have much more testosterone than women, and they develop heart disease about 10 years before their female counterparts. Like other muscle cells, cardiac muscle cells have receptors that bind male hormones. Animals that are given testosterone develop enlarged hearts. Athletes who abuse testosterone and other androgenic steroids have a sharply increased risk of high blood pressure, heart attack, and stroke. And in high doses, testosterone can have a negative effect on cardiac risk factors, including HDL (“good”) cholesterol levels.
The fact that large amounts of testosterone harm the heart and metabolism doesn’t necessarily mean that physiological amounts are also harmful. In fact, research is challenging these old dogmas. It’s hard for scientists to study possible new risk factors for heart disease. One reason is that there are so many cardiac risk factors, including family history, age, gender, blood pressure, cholesterol, blood sugar, obesity, smoking, exercise, and personality.
It’s also hard for scientists to study testosterone. There is an exceptionally wide range of normal values. Healthy men can have testosterone levels between 270 and 1,070 nanograms per deciliter (ng/dL). Heart disease and testosterone are mighty complex on their own, and studies that evaluate the two together are more complex still. Scientists who undertake these daunting investigations must account for all the things that influence heart disease and all the variables that affect testosterone.
With all these pitfalls, it’s not surprising that more research is needed to fill in all the blanks. Still, even if current information can’t tell us if testosterone can protect a man’s heart, it can dispel fear that physiologic levels of the hormone are toxic.
In high doses, androgens tend to raise LDL (“bad”) cholesterol levels and lower HDL cholesterol levels. That’s one of the things that gave testosterone its bad reputation. But in other circumstances, the situation is very different. Men who receive androgen-deprivation therapy for prostate cancer drop their testosterone levels nearly to zero, and when that happens, their cholesterol levels rise. Even within the normal range, men with the lowest testosterone levels tend to have the highest cholesterol levels.
Diabetes is another important cardiac risk factor. Prostate cancer treatments that lower levels of testosterone produce insulin resistance and increase the risk of diabetes. Obesity increases the risk of both diabetes and heart disease. Men with low testosterone have more body fat and more of the abdominal fat that’s most harmful than men with higher hormone levels, but since obesity itself reduces testosterone, it’s not clear which is the cause and which the effect.
Peripheral artery disease (PAD) is an important form of atherosclerosis in its own right and it also signals an increased risk for heart disease. A Swedish study of over 3,000 men with an average age of 75 linked low testosterone levels to an increased risk of PAD. At present, the hormone does not appear linked to hypertension or inflammatory markers.