For many middle-aged and elderly men, low libido, depressed mood and a lack of energy may just be the signs of normal aging -- and not low testosterone levels.

That's the conclusion of a new study that found only about 2 percent of men between 40 and 79 would qualify for a strict diagnosis of so-called late-onset hypogonadism, sometimes called "male menopause."

Earlier studies had indicated the diagnosis was much more common, and millions of prescriptions are written every year in the U.S. to help men with "Low T," as one drugmaker refers to the controversial condition. (See Reuters Health story June 8, 2010.)

Based on a random sample of more than 3,000 European men, British researchers found that only three symptoms -- fewer morning erections, fewer sexual thoughts, and erectile dysfunction -- were consistently related to low levels of the male sex hormone.

As one press release put it, the "researchers unzip symptoms" of the condition.
The authors suggest these sexual problems, in addition to a testosterone level of less than 3.2 nanograms per milliliter of blood, need to be present to identify late-onset hypogonadism. That level is about half of the "low normal" level in middle-aged men.

"The application of these new criteria can guard against the excessive diagnosis of hypogonadism and curb the injudicious use of testosterone in older men," Dr. Frederick Wu of the University of Manchester, United Kingdom, and colleagues write in the New England Journal of Medicine.

The study, published on Wednesday, is the first to identify key symptoms of the condition. It also shows that six other symptoms -- including fatigue and a lack of strength -- are common in men with dwindling hormone levels, although they are not as consistent as the sexual issues.

Still, many of the problems often tied to lo testosterone, like changes in sleeping patterns or anxiety, had no relation to the hormone. Even the sexual symptoms strongly tied to it were quite frequent in men with normal levels. For instance, almost a third of men said they could either never or only sometimes maintain an erection during sex.

"This study is quite significant in that it has a large number of patients," Dr. Martin Miner, co-director of the Men's Health Center at The Miriam Hospital in Providence, Rhode Island, told Reuters Health in an e-mail. Dr. Miner not involved in the new study.

Apart from its role in sexual problems, he said, low testosterone can be a marker for problems like obesity and diabetes, and is important for overall health.

Researchers who study male hormone deficiency, he said, believe the condition is "a 'real medical problem,' not one promulgated by pharma."

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