I have been reviewing John Brinkley’s goat gland scam for a presentation on medical frauds. In an era before the isolation of the hormone testosterone, Brinkley transplanted goat testes into human scrotums in an attempt to treat impotence and aging. We are more sophisticated today … but not much. Longevity clinics and individual practitioners are offering testosterone to men as a general pick-me-up and anti-aging treatment. Their practice is not supported by the scientific evidence.
Men’s testosterone levels drop as they age. According to a review article in the New England Journal of Medicine
the decrease in testosterone in men occurs moderately and gradually over a period of several decades. The serum total testosterone concentration decreases from a mean of about 600 ng per deciliter (20.8 nmol per liter) at 30 years of age to a mean of about 400 ng per deciliter (13.9 nmol per liter) at 80 years, although the range is wide at all ages. In one study, approximately 20 percent of men older than 60 years of age had total serum testosterone concentrations that were below the normal range for young men.
An essential but still unanswered question is whether this decrease in the testosterone concentration is physiologic, perhaps conveying a benefit, or pathologic, causing harm.
Other things happen as men age, and a simplistic, hopeful approach is to blame many of the consequences of aging on decreased testosterone levels and to use replacement therapy to bring the levels back to those of healthy youth. That approach is not science-based. Science only supports raising testosterone levels in patients who have specific problems attributable to abnormally low levels.
A recent article in JournalWatch reviewed the subject with reference to three new studies.
A July 2010 article in the NEJM by Wu et al. found that the only symptoms that correlate to low testosterone levels are poor morning erection, low sexual desire, and erectile dysfunction. Other psychological and physical symptoms correlated poorly with low testosterone levels. Total testosterone levels were sufficient for diagnosis; free testosterone levels did not add to diagnostic accuracy.
An article in the Journal of Clinical Endocrinology and Metabolism by Krasnoff et al. found that total testosterone was not associated with mobility limitation, subjective health, or any physical performance measures, whereas free testosterone was associated with subjective health and some (but not all) physical performance measures. Low baseline free testosterone levels were associated with subsequent decline in mobility but not in subjective health. JournalWatch editor Dr. Alan Brett comments that this study
shows correlations between free testosterone and some measures of physical performance; however, findings were mixed, and significant associations in observational studies do not necessarily indicate cause-and-effect.
A third study by Basaria et al. published in the New England Journal of Medicine studied older men with limitations of mobility to see if testosterone supplementation would improve mobility by increasing muscle mass and strength. This trial was stopped early because of a higher rate of cardiovascular events in the testosterone group compared to the placebo group.
These studies — considered alongside other recent studies in which testosterone supplementation did not yield impressive results in frail older men or in healthy older men — argue against indiscriminate use of testosterone as an “anti-aging” drug. This conclusion is supported by a new practice guideline from the Endocrine Society.
Testosterone is not harmless. The Mayo Clinic website lists several adverse effects of testosterone: sleep apnea, elevated red blood cell count, heart disease, acne, benign prostatic hypertrophy, breast enlargement, reduced sperm production, and shrinkage of testicles. Mentioning a risk of testicular shrinkage in the infomercials would put quite a dent in sales, I imagine.
Meanwhile, Suzanne Somers recommends testosterone for everyone: both men and women. On the Oprah website, readers provide testimonials:
Just ask my husband who take [sic] testosterone daily thanks to Suzanne’s books.
The unsupported opinions of celebrities and longevity opportunists versus the evidence of science-based medicine: take your pick.
This article was originally published in the Science-Based Medicine Blog.