A University of Iowa researcher is investigating the benefits of hormone replacement in older men.

Moshe Wald recently published a review of testosterone replacement studies in the Journal of Andrology, which publishes research findings on male reproductive tracts. Wald believes that testosterone replacement therapy might improve bone mineral density, libido, erectile function, mood and muscle mass in men with low testosterone levels.

Male hormone replacement therapy has been around at least 20 years by injection, but the therapy recently expanded to include gels, patches and formulations placed on the inside of the cheek.

Wald says the therapy is similar to hormone replacement medication given to women to treat symptoms of menopause, but it has significant differences.

Testosterone levels in men decrease as men age, usually after age 40. Unlike women, who experience changes at menopause, not all men exhibit symptoms of reduced testosterone levels.

Wald says the most common testosterone-related symptoms are sexual problems. Other problems include decreased energy levels, depression and memory lapses.

The key issue Wald's research showed was that testosterone replacement therapy "is not an automatic thing" for men with testosterone deficiency, he says.

Wald says testosterone can make prostate cancer flourish, so it's important to screen men before continuing with therapy. In high doses, it also can cause liver and fertility problems.

"We don't want to treat just the testosterone deficiency number, but instead identify those who actually have symptoms due to low testosterone," says Wald, an assistant urology professor at the University of Iowa Carver College of Medicine.

An estimated 13 million men in the United States experience testosterone deficiency, but Wald says he does not know how many would benefit from treatment. While therapy may help treat erectile dysfunction, he says, it would not replace drugs such as Viagra or Cialis in all cases because other factors may cause the condition.

The study did not recommend one type of treatment over another, but Wald recommends patients consider topical preparations because injections do not provide a consistent testosterone level.