Men have long accepted the fact that women can be emotionally and physically whipsawed by hormonal changes that come in midlife.

But now middle-aged men have begun to admit they, too, can experience hormonal shifts that affect many aspects of their lives such as sexual function and drive, muscle and bone strength, mood, mental acumen and energy.

Some call it male menopause, or "manopause."

"It's an easy way for men to understand or categorize what's going on," says Dr. William H. Haney, a physician who tries to keep up with the emerging medical treatment of aging men.

Menopause means a pause or cessation of the menstrual cycle. Of course, men don't have menstrual cycles and thus can't stop having them.

But testosterone does decline in men, just far more gradually than estrogen declines in women.

Other names given to this decline are andropause, referring to a deficiency in the production of androgens, a group of hormones of which testosterone is one.

Another term, far less popular with the public, is late onset hypogonadism. Still another is androgen deficiency of the aging male.

HORMONAL SHIFT

Because the decline of hormones in men is long and slow, men can be unaware of the changes their bodies and minds are undergoing. But television commercials and other media messages have raised awareness, stimulating men to talk to their physicians.

"There is more awareness of the symptoms and signs of testosterone decline and what it may do," says Dr. Stephen Winters, chief of endocrinology, metabolism and diabetes at the University of Louisville. He has had a career interest in male hormones and how they work for about 30 years.

"At one time, men who had sexual dysfunction were unwilling to admit that they had a problem and unwilling to talk to their physician, and usually their physician was totally uneducated and unable to help the patient in any way," he says.

Men are turning to doctors not only for help with erectile dysfunction but also with the issue of their low interest in sex, says urologist Dr. J.C. Trussell, expert on male menopause at Penn State Hershey Medical Center.

But complaints aren't just about sex. Haney says he's also hearing from men who say they are "fatigued and tired and can't make it through the day."

Dr. Robert S. Tan, author of "The Andropause Mystery" (AMRED Publishing, 2001), says he has seen a shift in the major complaint of men with low testosterone away from sex-drive problems.

"Now lethargy and fatigue are the most dominant complaint," Tan says. "They also can't concentrate, can't focus."

Tan, a Houston-based family physician and gerontologist, screens for hormone deficiencies and treats them when they are the underlying cause of a patient's problems.

TESTOSTERONE TESTS

Men's testosterone levels begin to drop at about age 30 at a rate of about 1 percent a year.

By about age 55, about one in three men fall into the low testosterone range, Tan says.

Not every man experiences symptoms from this decline, just as not every woman experiences symptoms from menopause.

But for men who do have complaints such as mood swings, depression and low sex drive, Tan has to determine if they are due to hormonal changes, clinical depression or the psychological impact of a midlife crisis. A physical exam and patient history help him determine if there is another possible cause such as alcohol abuse, the use of certain drugs or diabetes.

Blood tests can determine if the man's testosterone is below 300 nanograms per deciliter of blood, which is considered below normal.

But normalcy differs in individuals, so Tan, Haney and others recommend that men get their testosterone levels measured at about age 40 so they have a baseline by which to compare later measurements as they age.

TREATMENT

Treatment, when indicated, involves testosterone replacement therapy, which takes the form of a gel, patch or injection. Men taking hormones must be monitored closely. For one thing, testosterone can stimulate the prostate gland to grow. It also can stimulate the growth of any existing prostate cancer or breast cancer in a man.

Tests for liver or heart damage also must be done. Testosterone raises the number of red blood cells, increasing the risk of blood clots, heart attack and stroke.