TweetTIREDNESS, depression and lack of libido all seem inevitable parts of male aging, but what if an age-related lack of testosterone is at the root of all these symptoms? Increasingly, doctors say such an "andropause" exists and that its effects may go beyond feeling a bit tired - obesity and diabetes also appear to be linked. The good news is that testosterone supplements might help treat the problem.
Though testosterone is sometimes prescribed for ageing men in Europe and the US, until recently even the existence of andropause was considered controversial. Treating it was seen by many as unnecessary and potentially harmful because of concerns that testosterone supplements could contribute to prostate cancer by driving the growth of cancerous cells.
Now that attitude is starting to change. While many researchers and doctors still dislike the use of the word andropause - because it implies equivalence with menopause and yet does not affect all men - there is an acceptance that testosterone levels decline with age, resulting in testosterone deficiency - or late-onset hypogonadism (LOH) - in around 20 per cent of men over 65. "Age-related declines in testosterone are real," says Adrian Dobs of Johns Hopkins University in Baltimore, Maryland. "If a man has signs of hypogonadism then treatment should be considered."
Meanwhile, a handful of recent studies have linked low testosterone to the development of type 2 diabetes, obesity and cardiovascular disease. Other research indicates that some of the fears about testosterone supplements increasing the risk of prostate cancer may have been unfounded (See "Doesn't testosterone drive cancer?").
As a result, the International Association for the Study of the Aging Male, the International Society of Andrology, the European Association of Urology and the American Society of Andrology have updated their guidelines on who to screen for testosterone deficiency and how to treat it (Journal of Andrology, DOI: 10.2164/jandrol.108.006486).
In particular, they recommend measuring testosterone in all men who have both type 2 diabetes and symptoms of testosterone deficiency (see list of symptoms), and in those with erectile dysfunction or low libido. "This is a major change," says Andre Araujo, director of epidemiology at the New England Research Institutes in Watertown, Massachusetts. "That puts a lot of people in the category of being screened for low testosterone."
"It is going to pick up a lot of men with low testosterone who previously would have been sat at home without their doctor investigating it," says Hugh Jones, professor of andrology at the University of Sheffield, UK. That in turn means many more men could be given hormone replacement therapy.
The authors of the guidelines stress that, unlike menopause in women, not all men experience andropause and only those who show symptoms of testosterone deficiency should be considered for therapy. However, they also emphasise the role testosterone may play in causing these symptoms. In the case of erectile dysfunction, doctors are realising that drugs like Viagra, which increase blood flow to the penis, may not work if men also have low testosterone. Meanwhile, there is now strong evidence that low testosterone is linked with diabetes and obesity, and some evidence that boosting testosterone can alleviate the symptoms of diabetes.
"There are wide-reaching effects of testosterone on metabolism and vascular health," says Jones. He has shown that giving a testosterone gel to men who have both type 2 diabetes and testosterone deficiency improves their sensitivity to insulin, the hormone that controls blood sugar levels, in a study that was funded by ProStrakan of Galashiels, UK, a company that sells testosterone gel. Jones believes that the guidelines do not go far enough and suggests measuring testosterone levels in all men with diabetes, regardless of whether they also show symptoms of testosterone deficiency.
But this is controversial. Araujo says it can be difficult to disentangle whether low testosterone is a cause or a symptom of diabetes, so there is no evidence that boosting testosterone will be of any benefit to men who have no symptoms of deficiency. "There is no point in screening men for low testosterone at that point - levels will be low as a consequence of their diabetes," he says.
Eberhard Nieschlag of the University of Münster in Germany, who edited the new guidelines, raises the possibility of giving testosterone to kick-start weight loss or alleviation of diabetes symptoms - but then stopping treatment. "If you give testosterone to a man who lacks it, it is much easier for him to lose weight, but this should by no means become a treatment for life," he says.
All the experts contacted by New Scientist also warn against using testosterone supplements as a substitute for weight loss, healthy eating or conventional diabetes drugs, especially because treating the causes of the underlying disease may cause testosterone to rise back to normal on its own. "It is important to treat the underlying disease as well," says Dobs.