Subnormal testosterone levels most prevalent in obese men with diabetes

Issue: May 2010

Fifty percent of obese men with diabetes and 40% of obese men without diabetes aged 45 years and older have subnormal concentrations of free testosterone, new data revealed.

Researchers noted an inverse relationship between BMI and free testosterone concentrations, and they said obesity is likely the condition “most frequently associated with subnormal free testosterone concentrations in males.”

Data were analyzed using the Hypogonadism in Males (HIM) study, a U.S.-based, cross-sectional analysis of the prevalence of hypogonadism in men aged 45 years and older. The researchers measured free testosterone, total testosterone, bioavailable testosterone and sex hormone-binding globulin concentrations of 1,849 men (398 had diabetes).

Overall, 35% of men had subnormal free testosterone concentrations.

However, the mean free testosterone concentration of men with diabetes was significantly lower compared with men without diabetes. The average decade of free testosterone concentrations was 8.4 pg/mL per decade for men with diabetes vs. 7.8 pg/mL per decade for men without diabetes.

The researchers noted a significant decline in free testosterone concentrations with BMI in men with diabetes vs. men without diabetes: 58.8 pg/mL vs. 62 pg/mL for lean men; 56.9 pg/mL vs. 60.9 pg/mL for overweight men; 50.7 pg/mL vs. 55.5 pg/mL for obese men; and 45.1 pg/mL vs. 51.1 pg/mL for morbidly obese men.

The prevalence of subnormal free testosterone concentrations was 44% for lean men with diabetes, 44% for overweight men, 50% for obese men and 55% for morbidly obese men. Among men without diabetes, the prevalence of subnormal concentrations was 26% for lean men, 29% for overweight men, 40% for obese men and 49% for morbidly obese men.

Further, the prevalence of subnormal free testosterone levels was similar for men with diabetes treated with diet, metformin, sulfonylureas, thiazolidinediones and insulin.

Free testosterone concentrations were negatively and significantly associated with age, BMI and sex hormone-binding globulin (P<.001), according to the researchers.

“In view of the high rates of prevalence of subnormal free testosterone in patients with obesity or diabetes, the concentrations of free testosterone should be measured in these populations, especially when these conditions occur concomitantly,” the researchers concluded in a study published online ahead of print. – by Katie Kalvaitis

It is important to put these new data in proper context. This is the largest study to date defining the prevalence of hypogonadism, as defined by free testosterone, in obese men with and without diabetes. This is a relevant issue, in terms of the epidemic that currently exists in the United States, whereby 31% of all adult men are categorized as obese.

The main finding of this study that 40% of all obese men who do not have diabetes and 50% of obese men who have diabetes have abnormally low free testosterone is the take-home message. These data certainly warrant diagnostic testing and incorporation of a metabolic work-up that includes total and free testosterone for this population. The reasoning behind that is multiple. One cannot preach ‘lose weight and exercise’ without trying to ascertain if the person is hypogonadal and, thus, experiencing an obstacle to achieve their desired results, which can be easily diagnosed with a blood test. Furthermore, there are excellent epidemiologic data that demonstrate men with low testosterone have an increased mortality rate and increased risk for cardiovascular events, independent of other risk factors.

- Natan Bar-Chama, MD

Director of Male Reproductive Medicine and Surgery,

Associate Professor of the Department of Urology, Mount Sinai School of Medicine

Dhindsa S. Diabetes Care. 2010;doi:10.2337/dc09-1649.