Too much testosterone linked to diabetes and prostate problems

It may be linked with virility and sex appeal, but a high level of testosterone has a more serious side-effect, research suggests.

An increase in male sex hormone is linked to a raised risk of diabetes and an enlarged prostate gland, a study has found.

Saliva tests on 350 farmers of the remote Tsimane tribe in the Bolivian rainforest – where men generally have much less testosterone – found advanced cases of prostate enlargement were virtually non-existent.

They also had relatively low amounts of glucose in their blood, reducing the risk of developing diabetes, according to the findings published in the Journals of Gerontology: Medical Sciences.

By the time they hit 80, more than nine in ten men experience some degree of prostate enlargement – known medically as benign prostatic hyperplasia, or BPH – with about half requiring medical treatment.

Now anthropologists at the University of California, Santa Barbara, say findings among the Tsimane point to too much testosterone being a prime culprit.

Dr Benjamin Trumble said: ‘Abdominal ultrasounds show they have significantly smaller prostates – an age-adjusted 62 per cent smaller prostate size – as compared to men in the US.

‘We also know testosterone and androgens [male sex hormones] are involved because of studies showing that eunuchs and people who don’t have testes have very low rates of BPH. Some of the best pharmacological BPH and prostate cancer treatments involve reducing androgen levels.

‘We also know from our own previous research that Tsimane have relatively low levels of testosterone – about 30 per cent lower than age-matched US males – and they have very low rates of obesity and hypertension and heart disease and all the other diseases of acculturation, including metabolic disease.’

Despite having low testosterone overall, Tsimane men with higher testosterone levels, but that are still much lower than those of men in industrial populations, have larger prostates.

This has important implications for the millions of men who use supplements to counteract low testosterone. They may be putting themselves at risk for prostate enlargement.

The study did not test for prostate cancer but others have shown population differences in testosterone affect risk of the disease, according to Dr Trumble.

His colleague Professor Michael Gurven said: ‘In American men, testosterone levels decrease with age. It is easy to look at that pattern and think, “Well, if I want to reverse the ageing process, I only need to return to the high levels of testosterone of my vigorous youth”.

‘But there is probably a reason your body is producing less testosterone than it used to, and if you try to trick it and flood it with testosterone supplements, you may see some beneficial effects – people report feeling more energized, having a stronger libido – but at what cost?’

He suggested more long-term studies of testosterone-replacement therapy in men are necessary to ensure its safety and efficacy.

In addition to measuring prostate size, the researchers looked at the levels of glycated hemoglobin (HbA1c), a measure of long-term glucose exposure that in turn indicates the risk of diabetes, in the subjects’ blood.

Dr Trumble said: ‘Not one of the men in this study had HbA1c indicative of diabetes. These were all men with relatively low glucose levels.’

Professor Gurven explained the Tsimane are living under conditions more typical of our pre-industrial past, therefore the findings suggest that prostate enlargement is not necessarily an inevitable part of male aging but a product of our lifestyles.

Follow NEWS.am Medicine on Facebook and Twitter