Sunday, February 6, 2011

Even Low "Normal" Plasma Testosterone Levels Associated with 2.5x Higher Risk of Insulin Resistance

"Your levels are in range!" Did you ever have your doctor say that to you? It appears as if next time you hear that sentence, you better ask him "Where 'in range' are my levels, exactly?" At least, the results of a recently published study by Menendez et al. (Menendez. 2011) suggests that it might be worth digging somewhat deeper into this issue. Studying a cohort of 282 men (aged 36 to 85 years) who had "normal concentrations of total testosterone", the scientists found:
Serum concentrations of testosterone and bioavailable testosterone were negatively correlated with age, body mass index, waist circumference, blood glucose, glycated hemoglobin levels and insulin. Serum concentrations of total testosterone, bioavailable testosterone and SHBG were lower in men with glucose intolerance or diabetes than in those with normal glucose tolerance. After multivariate analysis, age and total testosterone levels were independent predictors of the presence of diabetes or glucose intolerance. The risk of glucose intolerance or diabetes mellitus was over 2.5 times higher in men with total testosterone levels in the lowest quartile than in those with total testosterone in the top quartile.
While the results of this study are certainly interesting and significant, it is unfortunately impossible to tell, whether glucose intolerance and diabetes reduce the natural production of testosterone, OR low testosterone levels reduce glucose intolerance and lead to diabetes. In other words: What comes first, low testosterone or glucose intolerance? Further research will be needed to answer this question, but if you want my opinion, I suspect that they just go hand in hand, i.e. a bad diet lowers glucose tolerance, high sugar reduces testosterone production, low androgen levels impair glucose tolerance etc. - a viscous circle.