Testosterone is predominantly produced by the testes in men. Small quantities are produced by the ovaries in women. The adrenal glands also produce small amounts in both sexes. Testosterone plays a key role in sexual functioning. Besides helping in the production of sperms, this steroid hormone also enhances libido, increases energy, helps produce red blood cells and protects against osteoporosis. Testosterone is an androgen and an anabolic steroid.

The blood levels of testosterone vary over a wide range. Testosterone levels gradually start declining during the third or early fourth decade of life at a constant rate. As a result, older men have significantly lower levels compared to their younger counterparts. Testosterone levels may also be low due to several diseases. The cutoff number is 250 ng/dL, levels below these are considered low.

What is the connection between testosterone and heart disease?

Low testosterone levels have been associated with increased risk of development and death from cardiovascular disease. In a recent study by Laughlin and associates, men with low levels and in the lowest quartile were 40% more likely to die early, especially from cardiovascular diseases. These findings were unaffected by age, lipid levels and other risk factors. The study involved 794 men aged 50-91 years, who were monitored for 20 years. The study was published in 2008 in the Journal of Clinical Endocrinology and Metabolism.

In 2007, results of the European Prospective Investigation into Cancer in Norfolk Study were published in Circulation. In this study, Khaw and associates monitored 11,000 patients aged 40-79 for their testosterone levels and death. They found that the latter were inversely related - low testosterone levels correlated with a higher rate of death from cardiovascular disease, cancer and all other causes.

In another study, Shores and colleagues, found that low testosterone levels were associated with an increased risk for mortality in male veterans. The male population was over 40 years of age and did not have prostate cancer. The study was done in Seattle and published in the Archives of Internal Medicine in 2006.

How does low testosterone cause cardiovascular disease?

The exact mechanism by which low testosterone causes cardiovascular disease is not clear, but there are several postulated mechanisms . Patients with low testosterone levels tend to have more visceral obesity. Visceral obesity is responsible for the apple shaped body (as compared to the pear shaped body, in which the fat is predominantly deposited in the hips and buttocks). More commonly, this is called the 'pot belly' or 'beer belly'. The visceral fat is packed in between the internal organs in the peritoneal cavity (abdominal cavity). In contrast the subcutaneous fat is found under the skin and the intramuscular fat in the skeletal muscle. Visceral fat is more metabolically active and synthesizes more heart unhealthy fatty acids, triglycerides, and adipokines than nonvisceral fat. Low testosterone is also associated with the development of metabolic syndrome and diabetes. In a study published in 2007, men in the lowest levels of testosterone were four times more likely to develop diabetes when compared to men with the highest levels. This data from the Third National Health and Nutrition Examination Survey, was published by Selvin and group in Diabetes Care. Patients with low testosterone levels have higher levels of insulin and triglycerides, both detrimental to the cardiovascular system.

Should you take testosterone to reduce heart disease?

There has been no scientific study in which testosterone replacement has been found to reduce heart disease. A study has just not been done. However, English and associates found that in patients with established coronary artery disease, testosterone replacement reduced exercise induced chest pain. This data was published in the European Heart Journal in 2000.

Summary

Testosterone is a predominantly male hormone produced by the testis and adrenals. It is responsible for libido in both sexes and the production of sperms in the male. It is also associated with increased energy, production of red cells and prevention of osteoporosis. Testosterone levels normally decline with age, with older men having a much lower levels than their younger counterparts. Low testosterone levels have been linked to an increased incidence of cardiovascular disease and mortality, and death from all causes. There is no published research on whether taking supplemental testosterone will reduce cardiovascular disease and death.



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