Reduced levels of testosterone, the male sex hormone, have previously been linked to decreased libido and lowered mood. Previously, low testosterone has also been found among men with type 2 diabetes. Now researchers in Australia report finding testosterone deficiency to be common among those with type 1 diabetes as well and it seems to be linked to insulin resistance. The findings raise the question of whether testosterone supplements might be useful for men with diabetes.
Previous research has revealed that testosterone deficiency is quite common in men who have type 2 diabetes and leads to low mood and decreased libido. It may also increase the risk of heart disease. Lowered testosterone has also been associated with insulin resistance, which is a known risk factor for complications in diabetes. Meanwhile, supplementation with testosterone improves insulin sensitivity, at least in short-term studies. Little is known of testosterone status among men with type 1 diabetes, however. Researchers at the University of Melbourne have surveyed testosterone levels among a group of men with both type 1 and type 2 diabetes to determine whether testosterone deficiency is a problem for both forms of the disease, or just in type 2, and how it might influence insulin resistance.
A group of 574 men with type 2 diabetes and 69 men with type 1 diabetes attending a diabetes clinic took part in the study. Most of the men had longstanding diabetes and complications like heart disease were common in the group. Total serum testosterone levels and circulating testosterone levels were measured, while insulin resistance was calculated from standard lab blood glucose and related tests.
As many as 43 percent of the men with type 2 diabetes had lowered total testosterone levels, with levels declining with age. And 57 percent had lowered circulating testosterone, again with lower levels among the older men. Few of the men in the type 1 diabetes group had low total testosterone and, in fact, the frequency of low levels was similar to that among healthy men. But one in five of the type 1 diabetics proved to have low circulating testosterone, which is significantly higher than would be found among healthy men.
Men with type 2 diabetes and low total and circulating testosterone were more likely to show insulin resistance. Among those with type 1 diabetes, low circulating testosterone was linked to insulin resistance.
This study is the first to show that low circulating testosterone is fairly common among men with type 1 diabetes. It is not clear whether insulin resistance causes low testosterone, or the other way round. Previous research has shown that testosterone supplementation can improve insulin sensitivity. Lifestyle measures, like weight loss, and medication designed to tackle insulin resistance may also raise testosterone levels. The relationship between testosterone, insulin, and diabetes is worthy of further investigation. The study raises the obvious question on whether testosterone replacement might increase insulin sensitivity among men with diabetes and thereby reduce the risk of complications. This could be tested in prospective clinical trials. However, testosterone may have an adverse effect on prostate disease and other conditions, so the risk and benefit ratio would have to be carefully assessed.