If the adverts are to be believed, testosterone supplements are a cure-all for men facing the unfortunate effects of middle age. The hormone is claimed to improve muscle strength, energy and sex drive. However, not only is there little evidence for this, several studies have found a link with heart disease.
Traditionally, testosterone was prescribed to men with abnormally low levels due to a congenital condition or damage to the testes from chemotherapy. Now, though, middle-aged men are being prescribed 鈥渢estosterone replacement therapy鈥� (TRT) to make up for the natural decline that often comes with age.
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In the US, the number of men being prescribed testosterone rose from 1.3 million to 2.3 million in the five years up to 2013, and the UK has seen a similar trend, although the numbers are far lower (see graph).
But in March, the US Food and Drug Administration cautioned that testosterone should , rather than general ageing, and confirmed by a lab test. The European Medicines Agency has .
The health bodies also asked manufacturers and prescribers of testosterone products to warn users about a possible risk of heart attacks and strokes after a number of studies showed an association. One trial was even terminated early due to an 鈥溾�� among participants. Worryingly, a 2013 analysis found that the level of cardiovascular risk reported varied, depending on whether the study was funded by the pharmaceutical industry.
One possible mechanism for testosterone鈥檚 effect on the heart could be through raising the number of red blood cells, which thickens the blood and can lead to dangerous clotting.
Another worry is prostate cancer, which feeds on testosterone; drugs blocking testosterone are sometimes used to stop the cancer spreading. A meta-analysis published in 2014 found no link with TRT in the short term, but .
鈥淭here鈥檚 an absence of data on the use of testosterone outside its key clinical application and yet some clinician enthusiasts, particularly private practitioners in the US, have just exploded testosterone prescribing to the point where it鈥檚 almost become mainstream,鈥� says Richard Quinton, an endocrinologist at Newcastle University, UK.
Part of the problem, at least in the US, is that men are not being properly tested before starting treatment, says an epidemiologist at the University of California, Los Angeles, who recently found that , and instead diagnosed men on the basis of a questionnaire about symptoms. Others relied on a single test, which is unreliable because levels vary dramatically throughout the day.
Low testosterone can be a result of health problems such as obesity and diabetes, and some researchers are examining whether TRT could help. But in these cases, says Quinton, it would often be more appropriate to treat the primary condition 鈥� for example, by losing weight. He questions whether age-related low testosterone 鈥� or 鈥渓ow T鈥� 鈥� is even a genuine condition. 鈥淪lim, healthy older men have similar levels of testosterone to healthy young men,鈥� he says. 鈥淪o probably 90 per cent of the fall in testosterone with age relates to just accumulating chronic diseases.鈥�
It鈥檚 a personal choice, says Greenland, but 鈥渋f I was somebody with any cardiovascular risk, I wouldn鈥檛 go there. Most of all, get tested 鈥� and not just once 鈥� before you embark on this.鈥�
This article appeared in print under the headline 鈥淭estosterone鈥�
