While testosterone is important to women – for maintaining a robust libido among other things – the “hunk hormone” remains a hallmark of male sexuality and drive.

Testosterone is often cast in a semi-negative light, associated with macho preening and posturing.

But testosterone is an essential to health – especially men’s health – and needs to be taken seriously as a medical topic.

Body levels of testosterone drop as we age, and likely explanations for the hormonal decline are several:

• Increased body fat in middle age stimulates activity of an enzyme called aromatase, which turns testosterone into estrogen, gives chubby men mini-breasts and leads to a syndrome called androgen-deficiency aging.
• Oxidative (free radical) stress on testosterone-producing organs and tissues. (Dietary antioxidants appear to help maintain testosterone levels.)
• Declining body levels of DHEA and other chemicals from which the body makes testosterone (i.e., testosterone precursors).

Low testosterone levels hurt hearts, promote diabetes

Low levels of testosterone are strongly associated with increased risk of metabolic syndrome and consequent risk of diabetes and cardiovascular disease (Bhasin S 2003; Boyanov MA 2003; Dobrzycki S et al 2003; Hak AE et al 2002; Zhao SP, Li XP 1998; Jeppesen LL et al 1996).

Metabolic syndrome is defined as having three or more of a half-dozen metabolic risk factors:

• Insulin resistance or glucose intolerance (the body can’t properly use insulin or blood sugar).
• Abdominal obesity (excessive fat tissue in and around the abdomen).
• High blood triglycerides, low HDL cholesterol and high LDL cholesterol: a state that fosters plaque buildups in artery walls.
• Elevated blood pressure.
• Pro-thrombotic state that promotes dangerous clots (e.g., high fibrinogen or plasminogen activator inhibitor–1 in the blood).
• Pro-inflammatory state (e.g., elevated C-reactive protein in the blood).

Testosterone injections appear to reduce insulin resistance and abdominal obesity, thus foiling two key factors in MS and the risk of cardiovascular disease (Bhasin S 2003; Boyanov MA 2003; Marin P et al 1992).

And supplemental testosterone may enhance memory and cognition in older men (Cherrier MM et al 2001; 2004).

Surprisingly, despite the hormone’s natural association with male sexuality, testosterone is an inconsistently effective treatment for impotence in most men (Isidori AM et al 2007). It often does more for women’s libidos than for men’s.

The effect of testosterone replacement on libido, strength, body composition (muscle-to-fat ratio), mood and energy appears to depend largely on a man’s natural level of the hormone.

Men with normal to low-normal testosterone levels typically show relatively little benefit after testosterone replacement therapy, while the benefits to men with low levels are often very substantial (Gruenewald DA, Matsumoto AM 2003; Wang C et al 2000; Tenover JS 1992).

A team at the University of Toronto reviewed the available evidence and published its findings earlier this year, which are worth quoting at length (Bain J et al 2007):

• “There is an expanding body of literature to support [testosterone replacement] treatment in a large subset of aging men, but there has not yet been a long-term placebo-controlled double-blind study of several thousand men to confirm the efficacy and safety of this treatment as indicated by shorter-term studies.
• “The absence of a long-term study has been used by governmental agencies as a limiting factor in providing full access and payment for this treatment in government-sponsored health care plans.
• “Short-term studies and 60 years of experience with testosterone therapy attest to its efficacy. Long-term studies are desirable, but it may take many years before results could be forthcoming.
• “There is no evidence to suggest that testosterone treatment increases the risk of prostate cancer or cardiovascular disease. Current evidence suggests, in fact, that testosterone treatment may be cardio-protective.”

British findings confirm preventive importance of testosterone

The risks of low testosterone levels to men appear even clearer, following publication of a study in 11,606 men aged 40 to 79 who participated in a Norfolk, England section of the huge European Prospective Investigation into Cancer (EPIC) study.

At the end of 10 years, the men with low testosterone levels had a greater risk of dying from any cause, including cardiovascular disease and cancer.

Researchers at the University of Cambridge and Royal Marsden Hospital in London drew blood samples drawn during the subjects’ initial visit between 1993 and 1997and measured the levels of testosterone and related aging factors.

The men’s medical status was tracked until 2003, including the causes of any deaths among them.

After adjusting the results for age, body mass index, and several other factors, men whose testosterone levels were in the top quarter were 41 percent less likely to have died, compared with men whose levels were in the lowest quarter.

And, after they excluded deaths recorded during the first two years of the study, the British team determined that the men’s risk of death from cancer or cardiovascular disease was inversely correlated with their testosterone levels: that is, more testosterone meant less risk of dying, and vice versa.

The authors noted that that higher testosterone levels are associated with lower, healthier levels of key cancer and heart risk factors, including inflammation and insulin.

Testosterone’s documented ability to protect against cardiovascular disease could stem from its effects on these factors, or by its ability to enhance two key influences on risk of heart attack and sudden cardiac death: endothelial (artery lining) function and coronary vasodilation (keeping arteries open).

What can you do to raise low testosterone levels?

Antioxidants may boost testosterone levels modestly, so it would make sense to be sure that you are getting the US RDA for the three most-studied essential antioxidant nutrients: selenium (200 micrograms mcg), vitamin A (5000 IU), and vitamin E (400 IU).

There is a long list of nutrients and herbs reported to enhance testosterone production, or boost signs associated with it, but the evidence for these claims is generally weak or lacking.

The only proven remedy is testosterone replacement therapy, which must be prescribed by a medical doctor, following tests to determine need. The hormone can be delivered orally, via muscle injection, or by use of a skin patch (transdermal system).

Men are often told that testosterone replacement therapy could increase the risk of prostate disease, including enlarged prostate (benign prostatic hypertrophy or BPH) and prostate cancer.

But the published evidence indicates that high testosterone levels are not associated with increased risk of prostate cancer.

In fact, low testosterone levels do not reduce the risk of prostate cancer, while high levels are associated with a reduced risk of aggressive prostate cancer, and have no effect on the risk of non-aggressive prostate cancer (Morgentaler A 2006; Severi G et al 2006).

In contrast, high levels of estrogen, have been linked to BPH, and estrogen appears to promote enlargement of the prostate gland (Shibata Y et al 2000; Gann PH et al 1995; Krieg M et al 1993).

NOTE: Testosterone replacement is contraindicated in men with carcinoma of the breast or known or suspected carcinoma of the prostate, as it may cause rapid growth of these tumors. Hormone therapy is also inadvisable in men with severe BPH-related bladder outlet obstruction. Use of testosterone by men with normal levels to boost athletic performance is potentially dangerous.

Sources

• Anderson RA et al. The effects of exogenous testosterone on sexuality and mood of normal men. J Clin Endocrinol Metab. 1992 Dec;75(6):1503-7.
• Bain J, Brock G, Kuzmarov I; International Consulting Group.Canadian Society for the Study of the Aging Male: response to health Canada's position paper on testosterone treatment. J Sex Med. 2007 May;4(3):558-66.
• Barrett-Connor E et al. Bioavailable testosterone and depressed mood in older men: the Rancho Bernardo Study. J Clin Endocrinol Metab. 1999b Feb;84(2):573-7.
• Barrett-Connor E et al. Endogenous sex hormones and cognitive function in older men. J Clin Endocrinol Metab. 1999a Oct;84(10):3681-5.
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• Cherrier MM et al. Relationship between testosterone supplementation and insulin-like growth factor-I levels and cognition in healthy older men. Psychoneuroendocrinology. 2004 Jan;29(1):65-82.
• Cherrier MM et al. Testosterone supplementation improves spatial and verbal memory in healthy older men. Neurology. 2001 Jul 10;57(1):80-8.
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