To most people, the term "steroids" refers to performance-enhancing drugs known scientifically as anabolic steroids. These synthetic drugs mimic the male hormone testosterone, causing increased muscle mass. Anabolic steroids should not be confused with corticosteroids, a group of medicinal steroids commonly used to reduce excessive inflammation in the body.

While anabolic steroids have some important medical uses, the desire to enhance athletic performance has spawned illegal, unsupervised use and abuse of these drugs. Numerous side effects can occur with anabolic steroid use. Many involve the reproductive system and typical male or female features, among others. Some side effects are reversible when use stops, but others are permanent or life-threatening.

Male-Specific Side Effects

The testicles normally produce testosterone and sperm. Taking anabolic steroids creates an artificial excess of male hormones in the body. This causes the hormonal feedback system of the body to tell the testicles to slow down.

As a result, men who use steroids often experience shrinkage of the testicles, decreased sperm production, and even impotence and infertility. These effects are usually reversible if steroid use stops. Under the influence of the excess male hormones, balding can occur, and the prostate gland might enlarge and cause difficulty passing urine. Because the body converts a portion of the circulating anabolic steroids into the female hormone estrogen, men who use steroids also commonly develop enlarged breasts -- an effect that is usually permanent.

Female-Specific Side Effects

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Women who use steroids often develop masculine features due to these testosteronelike hormones. In addition to increased muscle mass and decreased body fat, women might develop a deeper voice, facial and body hair and male-pattern baldness, all of which are usually permanent. Breast size might decrease, the clitoris might enlarge and the lining of the vagina may shrink, effects that also tend to be permanent. The menstrual cycle is often disrupted, typically causing light, irregular or absent periods. Disruption of normal hormonal systems can even lead to infertility. These menstrual and fertility problems are usually reversible if the drugs are stopped.

Cardiovascular Effects

The effects of steroid use on the cardiovascular system are some of the most serious 4. The blood thickens from overproduction of red blood cells, forcing the heart to work harder. Over time, the extra workload may lead to heart enlargement and possibly failure. Steroids also increase blood levels of "bad" cholesterol, which promotes formation of fat deposits called atherosclerotic plaques that can clog vital arteries. Plaques increases the risk for heart attack and stroke.

The risk is further increased because steroids make the blood more likely to clot inside arteries -- particularly where plaques have formed. Clot formation at the site of a plaque frequently triggers a heart attack or stroke.

Liver Effects

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Damage to the liver is another side effect of steroids. The liver processes most drugs that pass through the body, and high doses can overwhelm the liver and alter the level of liver enzymes involved in drug metabolism. The skin and whites of the eyes may turn yellow, a condition called jaundice. Intense itchiness typically accompanies steroid-induced jaundice.

Some steroids might cause the growth of cysts and tumors in the liver, and cases of liver cancer have been reported. It is thought that the steroids bind to receptors in liver cells, activating genes that regulate cell growth. This leads to unregulated growth of liver cells, producing a tumor.

Effects on Other Systems

Steroids affect the body in several other ways. They stimulate oil glands, leading to oily skin and development or worsening of acne. Steroids might weaken the ligaments and tendons of the joints, increasing the likelihood of injuries.

If taken by adolescents, steroids can stunt growth because they cause premature closing of the growth plates in the bones. Also, because steroids are often injected, users are at an increased risk of infection for things infections such as hepatitis C and human immunodeficiency virus if needles or syringes are shared.

Psychological Effects

Anabolic steroids might affect mood and behavior. In some people, the drugs seem to increase aggressiveness, anger and irritability, sometimes described as "roid rage." This has been linked with reports of increased violence and criminal activity, according to the National Institute on Drug Abuse 2.

Extreme mood swings also appear possible, with users sometimes reporting high levels of energy and impulsiveness with taking the drugs, followed by depression and anxiety when cycling off. Paranoia and delusions -- beliefs not based in reality -- have also been reported in association with steroid use.