As in previous years, the 2012 Olympics likely will be marred by at least one doping scandal, experts predict.

Many athletes abuse human growth hormone and/or steroids to build muscle and strength. While elite athletes are in the spotlight, the problem is much greater in recreational athletes. For example, at least 1 in 16 high school students admits to using performance-enhancing steroids. And users rarely take just one kind of drug.

Why do athletes and young people do this? Are there any benefits? What are the risks? WebMD's FAQ is based on an Endocrine Society webinar featuring two experts on athletic doping:

    Alan Rogol, MD, PhD, professor of pediatrics at the University of Virginia
    Shalender Bhasin, MD, professor of medicine and chief of endocrinology, diabetes, and nutrition at the Boston University School of Medicine

What is human growth hormone?

Human growth hormone, HGH, is produced by the pituitary gland. It's not really a single hormone, Rogol says, but a mixture of several "isoforms" coded by several different genes.

Children do not develop normally if their bodies don't make enough growth hormone. Fortunately, researchers have used recombinant gene technology to produce large amounts of recombinant HGH, or rHGH, to treat them.

More recently, rHGH has been used for other reasons.

"It is supposed to be the magic anti-aging hormone," Rogol says, although he notes that there's little evidence that it works in this way.
Why would athletes take HGH?

HGH helps the body store and use energy in ways that might be helpful to athletes. And abusing it also makes athletes look more like athletes.

"Athletes take it because it breaks down fat and builds muscle," Rogol says. "And part of the issue is that bodybuilders like that ripped look, with lots of muscle but not much subcutaneous fat."

Athletes also believe that HGH helps the body recover more quickly from injury and allows them to train harder.

"But what is the evidence for all this? There really is very little," Rogol says. "Yes, it gives you more muscle and less fat. Those muscles may look big, but they are pretty weak."

Most athletes who abuse HGH take it along with testosterone. But in clinical studies of strength and endurance, HGH adds little to the boost in performance seen with testosterone.

These studies, however, were done in normal people. A difference that makes little difference to a normal person may mean everything to an elite athlete.

"Say you're running the 100-meter dash," Rogol suggests. "If you're just 1% better, you cannot tell the difference in an experiment. But for an elite athlete, that 1% improvement may mean the difference between winning a gold medal and never making it to the Olympics."

What are the risks of abusing HGH?

The short-term risks of rHGH are water gain and swelling, muscle pain, and joint pain. The only really serious short-term risk is an increase of pressure in the brain. This happens to about 1% of children who receive HGH replacement therapy.

In the long term, the risks of abusing rHGH are more serious. Muscles can become weak, there's a higher risk of heart disease, and there's a risk of developing high blood sugar and type 2 diabetes.
Are there tests to detect rHGH?

Yes. The most reliable test looks for evidence of the most common isoform of rHGH, called 22 kDa. This test measures the amount of 22 kDa and the amount of total HGH in the blood. In normal people the ratio of 22 kDa HGH to total HGH is about 0.6. If the ratio is over 1.0, an athlete is considered to be doping with rHGH.

There are drawbacks, however. Some people carry a gene that keeps HGH blood levels low. Even dopers test negative for rHGH if they have this gene.

And the test has to be done no more than 36 hours -- some say 24 hours -- after a person takes rHGH.

Other rHGH tests look for telltale "biomarkers" of body functions that have been altered by rHGH. Such tests have been used and have led to sanctions against athletes, Rogol says.
What are anabolic steroids?

Anabolic steroids are male sex hormones, or androgens. Androgens are the most commonly used performance-enhancing drugs. They account for half of all positive drug tests in the last decade, Bhasin says.

"Use has been growing since the 1980s. Elite athletes actually constitute a very small fraction of use," he says. "Many who use anabolic steroids use intramuscular injections. There are about 30 such compounds, although testosterone, nandrolone, and stanozolol are the most common ones."
Why would athletes use steroids?

Studies show that steroids increase muscle mass and strength. Strenuous exercise doubles these gains, Bhasin says.

"But do bigger muscles and more strength translate into better athletic performance? Athletes believe it does, but we scientists don't understand the mechanisms," he says. "Steroids may promote recovery from injury and allow higher training intensity. It may increase oxygen in the blood. There is some evidence it decreases reaction time and promotes hand-eye coordination."
What are the risks of abusing steroids?

There's a widely held belief that androgens are safe. Nothing could be further from the truth when abusing these drugs, Bhasin says.

He offers a long list of known side effects when misused:

    Suicidal, homicidal, and sudden unexplained deaths
    Prolonged shutoff of normal hormones. "All users for any length of time suppress their own testosterone production for months and sometimes for years after they stop using steroids," Bhasin says.
    Mood disorders and psychiatric disorders
    Cardiovascular and metabolic problems
    Liver toxicity
    Gynecomastia (enlarged breasts in men)
    Risks associated with injections, such as abscesses or HIV infection
    Risks of accessory drugs usually taken along with steroids
    Risks associated with excessive muscle gain
    Growth retardation in children

"I've been following and tracking steroid-related adverse effects and deaths," Bhasin says. "In one study, Scandinavian power-lifters had a risk of death five times that of matched controls."

Can steroid use by athletes be detected?

All known steroids except testosterone can be identified with urine tests. These tests are very sensitive and are very reliable. Testosterone is trickier to detect, but abuse can be detected with a urine test and confirmed with sophisticated lab tests.

"The problem is the tests detect the 28 to 30 compounds they were designed to detect. But the underground community keeps coming up with new compounds," Bhasin says. "There is a disturbing rise in materials that were never tested and were created solely for abuse."