If you've never heard of human chorionic gonadotropin, it's probably because you're not a woman trying to get pregnant or a man whose testicles have stopped functioning. Those are two common recipients of an HCG prescription. According to rumors, L.A. Dodger Manny Ramirez, who was just banned for 50 games by MLB, was using it for erectile dysfunction, but that doesn't necessarily ring true.

Most performance-enhancing drugs, such as anabolic steroids, work by increasing the levels of testosterone. These are synthetic "super-testosterone," which amp up muscle growth.

From a testing standpoint, anabolic steroids are easy to identify since they alter the ratio of the body's natural testosterone. Many PED tests compare the ratio of testosterone found in a player's urine sample to the normal ratio. When there is significantly more of one type of testosterone present than the other, it's clear that the home run record should have an asterisk.

If a player wants to avoid detection by such tests, taking human chorionic gonadotropin is a nice option. HCG, like anabolic steroids, increases the amount of testosterone in the body but it does so by forcing the body to work overtime to increase testosterone levels and, in doing so, maintains the "normal" ratios. By raising the levels but keeping the body's different forms of testosterone proportionally intact, HCG use may go undetected by many test methods.

See another reason why people take HGC after the jump.

Another possibility is that Manny was using steroids but didn't want whomever he showers with to notice the telltale signs. HCG is often used as a masking agent to block the unwanted side effects that result from using anabolic steroids, such as man boobs (gynecomastia), shrunken testicles, zits and hair/dreadlock loss.

Other drugs sometimes used by athletes to surreptitiously boost the body's production of testosterone include:

-- Tamoxifen or anastrazole -- these are normally used as part of the treatment for breast cancer.

-- Raloxifene -- used by many grandmothers and other post-menopausal women to protect them against osteoporosis.

The common denominator here is that athletes will use these because they force the body to boost testosterone levels. For more on the hows and whys of PEDs see "Steroids and HGH: How Do They Work?"

Dr. Ken Spaeth is a Harvard-trained physician and a faculty member at Mount Sinai School of Medicine in New York. He is also co-author of "The Bioterrorism Sourcebook." You can e-mail him your questions at askdrken@aol.com.