Brain, not fat, causes low testosterone.

• Position: Type 2 Diabetes - Brief article

It is not estrogen produced by body fat that causes low levels of testosterone in type 2 diabetic men, according to a University at Buffalo (N.Y.) study. Instead, the mechanism responsible for low levels of certain sex hormones is more complicated than originally thought, which will have implications for the development of effective treatments. The researchers suggest that, based on their findings, the mechanism likely originates in the hypothalamus, the part of the brain that controls hormones influencing appetite, sleep, moods, and sex drive.

In 2004, researchers first identified this syndrome of hypogonadism (low testosterone) in one-third of type 2 diabetic men that they studied. At that time, the conventional wisdom was that an enzyme expressed by body fat is increased in obese people, affirms lead author Sandeep Dhindsa, assistant professor of medicine, and senior author Paresh Danclona, distinguished professor of medicine.

"It was thought that that enzyme, in turn, increased estradiol levels in the blood, which...