Testosterone helps men reduce body fat and improves the way their bodies handle insulin. So low testosterone levels may have serious consequences for men with diabetes, suggests Sandeep Dhindsa, MD, of State University of New York at Buffalo.
"We are describing a new complication of type 2 diabetes. We are saying that the largest group of people who have [low testosterone] are diabetics," Dhindsa tells WebMD. "It means your pituitary gland, which controls all the other hormones in your body, is not working very well. We are talking about one-third of men with diabetes being at risk of high fat mass, low muscle mass, low bone density, depression, and erectile dysfunction."
Total Testosterone Vs. Free Testosterone
Previous studies have found that men with diabetes are more likely to have low testosterone than are men without diabetes, notes Glenn R. Cunningham, MD, professor of molecular and cellular biology and vice chairman for research at Baylor College of Medicine.
"People have looked at testosterone levels in diabetics a lot. A number of studies show a fairly significant percentage of diabetics have low testosterone," Cunningham tells WebMD.
But most of these studies, Dhindsa says, relied on measures of total testosterone. Total testosterone levels depend on the amount of a testosterone-binding substance in the blood (sex hormone binding globulin, or SHBG). Since men with diabetes have low SHBG levels, it was hard to know what these earlier findings meant.
Dhindsa and colleagues, however, used much more sophisticated tests that measure free testosterone in the blood of 103 men with type 2 diabetes.
"That gives more validity to this study than to some of the others," Cunningham says. "They did find somewhat higher prevalence of low testosterone than previously reported."
Low Testosterone In Diabetes: More Than Obesity
A man's testosterone levels drop as he ages. If he's obese, his testosterone levels drop even more. Diabetes accentuates these effects.
Indeed, the older and more obese men in the Dhindsa study did tend to have low testosterone levels. But many of the younger, leaner men had low testosterone, too.
The researchers found nothing wrong with the men's testes. Instead, they found evidence that the men's pituitary glands weren't making enough luteinizing hormone. That's the hormone that tells the testes to make testosterone.
Why is this a problem? Low testosterone levels are, of course, linked to erectile dysfunction. Low testosterone is linked to higher fat mass, particularly abdominal fat, which is particularly dangerous for people with diabetes because of its risk for heart disease. Low testosterone is also linked to low bone density, low lean muscle mass, depression, mood disorders, and cognitive problems. And low testosterone is linked to insulin resistance.
Advice To Men With Diabetes: Get Testosterone Test
Cunningham advises men with diabetes to get a testosterone test — free testosterone, not total testosterone — if they have any symptoms of sexual dysfunction.
Dhindsa advises men with diabetes not to wait for symptoms, but to get a testosterone test as part of their basic medical care.
"We are screening all diabetic men for low testosterone because the symptoms are very nonspecific," he says. "Anyone can have erectile dysfunction or a mood problem. And most diabetes patients with low testosterone do not have any symptoms. They are surprised to find they have low testosterone."
Testosterone replacement therapy is available. Will it help people with diabetes? That remains to be seen. Dhindsa and colleagues are giving the treatment to men with diabetes and low testosterone, but it's too soon to tell whether it's the right thing to do.
"The data are not sufficient to recommend testosterone replacement for men with diabetes," Cunningham says. "One of the things that could be important is when you treat a man with male sex hormone, it increases lean body mass and causes some decrease in fat mass. There is some issue whether testosterone might improve diabetic men's insulin sensitivity. The studies we have are not definitive."
Sources: Dhindsa, S. The Journal of Clinical Endocrinology & Metabolism, November 2004; vol 89: pp 5462-5468. Sandeep Dhindsa, MD, assistant professor of medicine, State University of New York, Buffalo. Glenn R. Cunningham, MD, professor of molecular and cellular biology and vice chairman for research, Baylor College of Medicine; associate chief of staff, Research Service, VA Medical Center, Houston.
By Daniel J. DeNoon
Reviewed by Brunilda Nazario, MD
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