The testosterone effect

While it was only recently that the relationship between cardiovascular fitness and testosterone was firmly established, evidence for the beneficial effect of testosterone has been scientifically suggested for almost 100 years. During World War I, for example, a Danish surgeon named Thorkild Rovsing removed the intact testicles of a recently killed soldier and transplanted them into the body of an old man suffering from gangrene. Inexplicably to physicians of the day, the gangrene healed.²¹

Decades later, leading testosterone researcher Maurice Lesser, M.D., of the Boston University School of Medicine published the results of 100 consecutive angina pectoris patients who were treated with testosterone for at least four months. Prior to their treatment, Lesser reported that each patient had a clearly defined diagnosis of angina based on their medical history. The results showed that 91% of the patients reported either marked or moderate improvement in the number of angina attacks as compared with the pre-treatment rate.²²

Following the Lesser studies, research into the cardiovascular benefit of testosterone erupted. Numerous researchers reported that cardiac function in elderly men with heart disease improved dramatically when treated with testosterone. Other studies found that testosterone effectively reduced blood pressure and improved vascular circulation.²³ As late as 1993, however, the reason for these effects remained unclear.

Finally, however, in 1994 Dr. Gerald B. Phillips at Columbia University College of Physicians and Surgeons discovered the answer while conducting a cross-sectional study of 55 men who were undergoing coronary angiography. At the time of the angiography, none of these men had ever had a heart attack or stroke. When serum testosterone levels from these men were analyzed, they revealed that as testosterone levels decreased, the degree of arterial occlusion increased. Phillips observed that low testosterone levels were associated with several risk factors for heart attack such as high insulin levels, abnormal glucose metabolism, low levels of HDL cholesterol and high blood pressure. Moreover, he further proposed that the converse was also true: testosterone protects against heart disease in men.²⁴

The research continues

Since Dr. Phillips published his findings, an enormous body of research has gone on to confirm the cardiovascular benefits of testosterone.

In one of the most comprehensive studies, researchers in the Netherlands evaluated the effect of low levels of testosterone in elderly men. Known as the Rotterdam Study, this population-based investigation examined the relationship between total and bio-available testosterone with aortic atherosclerosis among 1,032 nonsmoking men and women aged 55 years and over. For six years, baseline data on the subjects was collected and evaluated and upon final examination, researchers concluded that men with the lowest levels of total and bio-available testosterone had the highest risk for severe aortic atherosclerosis. Conversely, men with the highest levels of both total and bio-available testosterone were protected against atherosclerosis.²⁵ These results confirmed Dr. Phillips' finding that low serum testosterone is correlated with increased heart disease.

With a clear link between atherosclerosis and low levels of testosterone established, researchers have expanded their scope to examine the other cardiovascular benefits of this hormone. For example, recent studies have revealed that testosterone improves insulin sensitivity in healthy men, suggesting a role in preventing Type II diabetes.²⁶ Other studies have found that in men with angina, supplemental testosterone therapy not only clinically improves symptoms but also reduces objective measurements of ischemia (impaired blood flow).²⁷ Still more research has determined that testosterone induces vasodilatation and may be helpful in cases of chronic congestive heart failure,²⁸ is responsible for maintaining heart muscle protein synthesis,²⁹ and reduces the levels of harmful LDL cholesterol.³⁰

The other benefits of testosterone

While the relationship between youthful levels of testosterone and a healthy cardiovascular system cannot be denied, it is far from the end of the story. Research has slowly started to uncover many of the hidden benefits of testosterone, such as its effect on bone growth and stability, depression, obesity and libido.

Osteoporosis

Osteoporosis is a metabolic bone disease characterized by the serious loss of bone mass and microdisintegration resulting in an increased risk of fracture. Although more commonly associated with post-menopausal women, osteoporosis affects more than five million men in the United States each year.

Without a doubt, low testosterone is one of the major causes of osteoporosis in aging men. Researchers in Germany have recently published a report estimating that 50% of all bone fractures in males over 60 years old is a result of osteoporosis induced by low testosterone levels.³¹ Complementing that report, researchers in France studying the relationship between testosterone and male osteoporosis have found that by age 80, as much as 20% of the bone mass density of males was lost in part due to the lower levels of testosterone.³²

The mechanism behind testosterone's effect on bone mass and stability was the recent topic of study for a group of Canadian researchers. According to their report, low levels of testosterone indirectly diminished bone mass by extending the longevity, generation and activity of bone-destroying osteoclast cells. The explanation for this is simply that testosterone is an inhibitor of osteoclast function. Lowering the testosterone level removes this inhibitory effect and allows osteoclasts to resorb (breakdown) bone. This study suggests that by maintaining youthful levels of testosterone, osteoclast (bone degrading) activity and the subsequent loss of bone mass can be reduced. This effect of testosterone on osteoclast activity is also of vital importance in men receiving androgen deprivation therapy for prostate cancer. Such patients have biochemical evidence of immediate bone loss. The severity of this problem has led to the use of drugs that inactivate the osteoclast; these are called bisphosphonates. Common examples of oral bisphosphonates are Fosamax and Actonel, and of intravenous bisphosphonates are Aredia and Zometa.³³ When bisphosphonates are given, osteoclast activity is inhibited and bone formation is favored. It is important that such patients receive bone supplements such as Bone Assure to allow for healthy bone formation. This focus on testosterone and its effect on bone integrity is discussed and described in depth on the LEF internet site at www.lef.org and also at www.lefprostate.org.

Depression

A consistent finding in the scientific literature is that depression is frequently associated with low levels of testosterone.³⁴ However, because practicing physicians often have only a basic understanding of testosterone deficiency, many patients suffering from its effects are misdiagnosed. Furthermore, because of the misplaced stigma associated with testosterone, psychiatrists rarely consider testosterone replacement therapy as a viable course of treatment.

Unfortunately for the patient, a common side effect of prescription antidepressants is a suppressed libido. Those suffering from depression must then choose between this drug-induced reaction and a normal sex life. If more psychiatrists tested their patients' blood for free testosterone and prescribed natural testosterone therapies when appropriate, the need for antidepressant drugs could potentially be avoided.

At Harvard University, researchers recently conducted a study to compare levels of testosterone among HIV-positive men who had HIV-related weight loss. The researchers also gave some subjects injections of testosterone to find out if supplements of this hormone had an impact on feelings of depression. The researchers found that men who had low levels of testosterone were more likely to be depressed than men who had normal levels of this hormone. Moreover, when the depressed men received regular injections of testosterone their mood significantly improved.³⁵

Researchers at Columbia University also found evidence supporting a relationship between advanced age, low testosterone and depression. In their study, depressed men over 75 years-old were found to have on average 35 percent lower free testosterone levels than younger men. In addition, 25 percent of those tested were determined to be severely testosterone deficient. Treatment with supplemental testosterone resulted in a reduction of depressive symptoms, further demonstrating the antidepressant effects of testosterone.³⁶

Testosterone and obesity

Obesity is a vicious cycle. Fat cells are known to be a source of aromatase, the enzyme responsible for convert-ing testosterone into estrogen.³⁷ Low testosterone results in the formation of abdominal fat, which in turn causes more aromatase enzyme formation and thus even lower levels of testosterone. The result is one of the most common findings of researchers studying the relationship between testosterone and obesity: obese men have low levels of testosterone and extraordinarily high levels of estrogen.³⁸

This fact was again confirmed in a study recently published in Aging Male which stated that increased estradiol levels due to free testosterone aromatization is highly significant and positively related to body fat mass and more specifically to subcutaneous abdominal fat. Even more intriguing, the study found that obese men not only had a significantly lower testosterone level and higher levels of estradiol, but that their estrogen levels were greater than the average post-menopausal woman.³⁹

Since research has shown that boosting the testosterone decreases the abdominal fat mass, reverses glucose intolerance and reduces lipoprotein abnormalities in the serum, it is especially important for overweight men to consider some form of testosterone therapy.