Women are not the only ones who experience hot flashes, mood swings and the loss of sex drive.

Men between the ages of 40 and 55 are currently going through male menopause.

"Male menopause is the lowering of the male hormone testosterone that occurs naturally with aging," said Dr. John Morley, a gerontologist at Saint Louis University.

"I think it's quite a difficult problem for men to find out because symptoms are very unspecific," said Dr. Ugis Gruntmanis of UT Southwestern Medical.

Men going through menopause can experience muscle loss, osteoporosis, nervousness, fatigue, weight gain and low sex drive.

The big difference between men and women? Male menopause takes place over a period of maybe 10 to 20 years.

Male menopause can be diagnosed with a blood test. Studies show testosterone replacement can enhance libido and sexual function. It can also improve bone density and muscle mass.

A key concern is that this treatment may increase the risk of prostate cancer, but some men believe it's worth it.

Doctors are hoping a study will be done on testosterone replacement therapy. So far, the long-term risks aren't known.