CINCINNATI -- A team of scientists has discovered that a little-known molecule created in the intestine when soy is digested is a natural and powerful blocker of a potent male hormone involved in prostate cancer and male pattern baldness. In fact, the molecule, equol, completely stops in its tracks the male hormone dihydrotestosterone (DHT), which normally stimulates prostate growth and causes male pattern baldness.

"This molecule is remarkable," says Kenneth Setchell, PhD, director of Clinical Mass Spectrometry at Cincinnati Children's Hospital Medical Center, who first identified equol in humans 20 years ago. "These findings are of immense clinical importance because blocking the action of the potent androgen (male hormone) DHT has been one of the holy grails of the pharmaceutical industry as a strategy for treating prostate cancer and other related diseases. This natural metabolite made from soy isoflavones, which are found in high amounts in soybeans, does this very effectively."

The study, which tested the response to equol in rats, was conducted at Colorado State University, Brigham Young University, and Cincinnati Children's and appears in the April edition of Biology of Reproduction.

In recent years, the pharmaceutical industry has developed drugs that inhibit a certain enzyme that converts testosterone to DHT. Unfortunately, these drugs have side effects. Equol, on the other hand, doesn't prevent DHT from being made but prevents it from functioning. It puts "handcuffs" on DHT, preventing it from binding to the androgen receptor and thereby preventing the prostate from growing. This may be particularly important for men who have been diagnosed with either an enlarged prostate (benign prostatic hyperplasia, or BPH) or cancer of the prostate.

"Directly binding and inactivating DHT without influencing testosterone gives equol the ability to reduce many of the harmful effects of androgens without affecting the beneficial ones," said Robert J. Handa, PhD, senior author of the study and professor in the department of biomedical sciences at Colorado State's College of Veterinary Medicine.

"The novelty of equol is that it both inhibits androgen hormone and influences estrogen hormone action," adds Edwin Lephart, PhD, professor of physiology and developmental biology and director of the Neuroscience Center at Brigham Young University. "We do not know of any other molecule that possesses these important biochemical properties."

Two experiments demonstrated that injections of equol into male rats reduced the size of the prostate. In one study, the testes of male rats were removed, thereby eliminating all DHT production. When investigators injected DHT into rats, their prostates grew. When they gave rats equol, nothing happened at all. When they injected rats with both equol and DHT, the equol prevented the DHT from functioning as it normally would – as a stimulator of prostate growth.

In other words, equol did not change hormone levels but completely blocked the effects of DHT in rats. This could explain why men in Japan, who eat more soy than American men but suffer equally from BPH as they age, rarely go on to have prostate cancer, according to Dr. Setchell. Several human studies have demonstrated the advantages of eating soy in reducing the risk of prostate cancer.

So far, research has established the relevance of DHT in the growth of male reproductive organs and, given the importance of DHT in the skin, it is possible that equol may offer a means of controlling hair loss and promoting healthy skin. The researchers have initiated further studies of equol to assess its potential as a treatment for a variety of other androgen-mediated conditions. The team has filed patent applications on equol and hopes to commercialize the technology.

The lead author of the study was Trent Lund, assistant professor in the department of biomedical sciences at Colorado State.