Recent Animal Studies
Two recent animal studies further document testosterone’s positive effects on the heart and arterial system.
One study published in December 2003 examined the coronary arteries of rabbits. Testosterone administration was found to relax the rabbits’ coronary arteries, which suggests that humans suffering angina could benefit from testosterone.15
Another study published in October 2003 investigated the impact of testosterone on myocardial ischemia-reperfusion injury and corresponding intracellular calcium metabolism.16 This is a way of simulating what happens when a person suffers an acute coronary artery occlusion (heart attack) and is able to be revived in a hospital.
The rabbits were first castrated in order to deplete testosterone, and were then given testosterone or placebo. After two weeks of treatment, the hearts were removed and placed on an artificial apparatus where they were deprived of blood flow (no blood flow ischemia) for 30 minutes and then re-perfused for 30 minutes. Compared to placebo, the recovery of contractile heart muscle function was greater in the testosterone-treated rabbits. Calcium overload influx into the cells was lower in the testosterone group compared to placebo. This is important because one of the irreversible effects of cardiac ischemia (caused by no blood flow to a portion of the heart) is excess calcium infiltration into cells that permanently damages the delicate intracellular machinery, thus making resuscitation impossible.
The scientists concluded: “Administration of testosterone significantly improves recovery from global ischemia.” For humans, this means that having adequate testosterone levels may significantly enhance the chances of being revived following a heart attack.
Testosterone and Prostate Cancer Risk
Many doctors are still under the impression that testosterone causes prostate cancer. The preponderance of evidence indicates otherwise.
Back in 1999, we wrote an extensive protocol describing how aging men could safely boost their free testosterone levels.17 Because there was such a strong perception that testosterone augmentation could increase the risk of prostate cancer, we did a MEDLINE search for all published studies relating to serum testosterone and prostate cancer. Of the 27 studies we found on MEDLINE, only five indicated that men with higher testosterone levels had a greater incidence of prostate cancer, whereas 21 studies found that testosterone was not a risk factor and one study was considered neutral. Thus, in 1999, the score was 21 to 5 in favor of testosterone not increasing prostate cancer risk.
Some recent studies have clarified this debate more definitively. A study published in December 2003 analyzed blood samples of 300 cases of prostate cancer diagnosed between 1987 and 1998 and compared them to 300 matched controls. Higher concentrations of testosterone were not associated with increased prostate cancer risk. In fact, men with the highest levels of free testosterone were 26% less likely to have prostate cancer than men with the lowest levels of free testosterone.18
A study published in January 2004 compared 708 men who were diagnosed with prostate cancer to 2,242 men who were not diagnosed with it. The results showed that higher levels of testosterone correlated with a decreased risk of prostate cancer. Men with the highest free testosterone levels were 18% less likely to have prostate cancer than men with the lowest levels.19
A study published in December 2003 was particularly revealing. A group of 75 men with low testosterone and a precancerous prostate lesion (called high-grade prostatic intraepithelial neoplasia) were administered testosterone replacement therapy for one year. The men all underwent prostate biopsy to rule out frank prostate cancer, and their blood was tested for prostate-specific antigen (PSA). After one year of testosterone drug therapy, these men did not have a significantly greater increase in PSA or risk of cancer than the men without precancerous lesions. The doctors concluded that testosterone replacement therapy is not contraindicated in men with precancerous lesions.20
In a study published in May 2003, a test that measures testosterone bioactivity in the blood was used to compare men with benign prostate enlargement to those with newly diagnosed prostate cancer. Men with prostate tumors had lower testosterone bioactivity. Levels of free testosterone did not differ between the two groups.21
Unfortunately, one new unpublished report contradicts the other four recently published positive studies. In this study, stored blood samples of several different hormones were measured in 111 prostate cancer victims out of a group of 759 aged men. The findings showed that higher levels of free testosterone resulted in a significant increase in prostate cancer risk. Higher levels of DHEA and other sex hormones did not result in increased prostate cancer risk. The doctors who conducted this study cautioned that men on testosterone replacement therapy should be advised that they might be increasing their risk of prostate cancer. Of course, the news media reported on this one negative study while ignoring the four recent positive studies.22
Flaws in Prostate Cancer Studies
Conventional medicine continues to focus on relatively narrow parameters when seeking to define disease risk factors. In other words, when evaluating the effects of higher testosterone levels on prostate cancer incidence, researchers fail to measure numerous other factors that may either increase or decrease one’s risk.
This means that findings from both positive and negative studies can be skewed because scientists do not take into account dietary and supplemental intake of nutrients shown to reduce prostate cancer risk, such as lycopene, vitamin D, boron, soy, vitamin E, fish oil, gamma tocopherol, selenium, and indole-3-carbinol. Other dietary factors—such as heavy consumption of saturated fats and high-glycemic foods that increase risk, and regular ingestion of fish, fruits, and vegetables that decrease risk—are also ignored when seeking to determine whether higher testosterone levels increase prostate cancer incidence.23-25
We do not want to criticize these researchers unfairly, as the costs of evaluating blood levels or consumption of nutrients and foods that affect prostate cancer risk are often beyond the financial limits of the grants that fund these studies. In fact, our organization has been a vocal critic of the paucity of government funding aimed at eradicating age-related diseases such as cancer. If more money were available to conduct prostate cancer research, many additional factors could be mea-sured when seeking to identify what aging men should be doing to reduce their risk.
In contrast to researchers who make general recommendations based on limited data, we at Life Extension advocate a much more comprehensive approach. We first examine all of the scientific studies on a particular subject, such as blood testosterone levels and prostate cancer incidence.
In this case, the preponderance of scientific studies (greater than 4 to 1) indicates that higher free testosterone levels do not result in greater prostate cancer incidence.26
We then look at results of the many blood tests we conduct to measure levels of free testosterone, estradiol, and PSA. When looking at these blood reports, it is hard to subscribe to the theory that higher levels of testosterone are a concern when so many men with prostate cancer are already testosterone deficient (by Life Extension standards).
To clarify this point, conventional doctors define low testosterone as being below standard laboratory reference ranges. We, on the other hand, view aging men who are in the lower one-third to one-half of normal reference ranges as being testosterone deficient. Laboratory reference ranges are based on “normal” population averages, and it is quite normal for aged men have low testosterone levels. Humans suffer devastating health consequences in their later years. To circumvent these “normal” pathological changes, we advocate aggressive approaches to counteract the effects of normalcy, including the negative effects associated with low testosterone.
Since prostate cancer is such a widespread problem, most Life Extension members are already taking nutrients and following diets that have been shown to significantly reduce the risk. As evidence accumulates indicating that higher testosterone protects men against a host of age-related disorders, fear of prostate cancer may not be an appropriate reason to allow one’s testosterone to remain at less-than-optimal levels. We must emphasize, however, that men with prostate cancer cannot take testosterone-boosting therapies because this hormone stimulates the proliferation of existing prostate cancer cells.