September 25, 2013

BARCELONA, SPAIN — Results from a small population-based observational study suggest there is an inverse relationship between serum testosterone levels and acute MI, specifically in men with diabetes.

In an analysis of 1109 men and women living in southwest Sweden, researchers reported that men with diabetes with the highest levels of testosterone had a 25% lower risk of acute MI when compared with diabetic men in the lowest quartile (p=0.02). Testosterone levels were not predictive of acute MI in men without diabetes nor in women with and without diabetes, however.

The Swedish study, presented here at the European Association for the Study of Diabetes (EASD) 2013 Meeting , included 538 men and 571 women over 40 years of age.

I would be very surprised if treating patients with low testosterone prevents cardiovascular events.

Dr Naveed Sattar (University of Glasgow, Scotland), who moderated the session at the EASD meeting, told heartwire the association needs further investigation before any causal links are firmly established. Hypotheses regarding testosterone's role in cardiovascular disease have been around a long time, he added, and other research has suggested testosterone is not a causal risk factor for cardiovascular events. The low testosterone levels "might simply be a reflection of something else that is going on," said Sattar.

Lead investigator Dr Bledar Daka (University of Gothenburg, Sweden) agreed, saying the study does allow anybody to draw firm conclusions and that replication studies are needed. However, the study did show a trend toward an inverse relationship between serum testosterone and acute MI in the overall population, although the result was significant only in men with diabetes.

"Low concentrations of serum testosterone levels have been shown to predict the risk of diabetes in previous observation studies," explained Daka, "and serum testosterone seems to have a vasodilatory effect on the coronary arteries. Low concentrations of testosterone are also associated with higher rates of mortality from cardiovascular disease in men."

After an average follow-up of 14.1 years, there were 64 acute MIs in men without diabetes and 49 events in women without diabetes, a statistically significant difference (14.2% vs 9.7%; p=0.02). There was no significant difference in the rates of acute MI between men and women with diabetes (20.8% vs 24.3%; p=0.45).

The baseline total testosterone level was 13.5 mmol/L in men and 1.00 mmol/L in women. For diabetic men with high levels of testosterone, those in the highest quartile, the risk of acute MI was significantly reduced (hazard ratio 0.75; p=0.006) even after adjustment for confounding variables, such as age. In women with diabetes and without diabetes, there was no association between serum testosterone levels and acute MI.

Sattar stressed that the study should be considered hypothesis-generating given the observational nature of the analysis.

"It could simply be that some of the factors are common to low testosterone and cardiovascular disease and that low testosterone is not causally a risk factor," he told heartwire . "We need to do some more observational and genetic studies to try to get at causality. If it still looks positive, then maybe we could try to develop well-designed intervention studies. I would be very surprised if treating patients with low testosterone prevents cardiovascular events, however."

The authors reported no conflicts of interest.


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