Last reviewed by Faculty of Harvard Medical School on December 30, 2010
By Harvey B. Simon, M.D.
Harvard Medical School
There was a time when a guy could open to the sports page and read about sports. Now it seems there is as much news about performance-enhancing drugs as batting averages. Human growth hormone is a favorite of jocks. It is also promoted as an "anti-aging" supplement. But can it help in either role? And what are its side effects?
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Growth Hormone: Up Close and Personal
Growth hormone (GH) is made by the pituitary gland and then secreted into the bloodstream. A complex mix of hormones produced in the hypothalamus (a part of the brain), intestinal tract and pancreas control its production.
GH boosts protein production, helps the body use fat, interferes with the action of insulin and raises blood sugar levels. GH also raises levels of insulin-like growth factor-1 (IGF-1). In children, GH stimulates the growth of bone and cartilage.
Blood levels of GH rise and fall throughout the day. Exercise, trauma and sleep raise GH. (That's why individual blood tests to measure GH levels are meaningless.) GH levels rise during childhood, peak during puberty, and decline from middle-age onward.
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GH is a prescription drug. It is given by injection to children who have a GH deficiency and to certain individuals with very short stature.
It is also approved to treat adults who are diagnosed with a GH deficiency due to a rare condition that affects the hypothalamus, pituitary gland, or both. Special tests are needed to diagnosis adult GH-deficiency. Individual random blood tests for GH levels are useless at best, and can be misleading at worst.
Adults with true GH deficiencies benefit from GH injections. They protect bones fractures, increase muscle mass, improve exercise capacity and energy, and reduce the risk of heart disease for these patients. But up to 30% of patients experience side effects, including fluid retention, joint and muscle pain, carpal tunnel syndrome (pressure on the nerve in the wrist causing hand pain and numbness) and high blood-sugar levels.
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GH Doping: Pain With No Gain
Some athletes use GH injections to get larger muscles, have more energy and enhance performance. The International Olympic Committee, Major League Baseball, the National Football League, and the World Anti-Doping Agency have all banned GH. Nevertheless, it's abuse has tainted many sports, including baseball, cycling, and track and field. Competitive athletes who abuse GH risk disqualification and disgrace.
How much do they gain in performance and are the health risks worth it? A team of researchers from California conducted a detailed review of 44 high-quality studies of growth hormone in athletes. The subjects were young, lean, and physically fit; 85% were male. A total of 303 volunteers received daily GH injections while 137 received the placebo shots.
After an average of 20 days, the subjects who received GH increased their lean body mass (which reflects muscle mass, but can also count fluid mass) by an average of four to six pounds. That's a big gain but it did not translate into improved performance. In fact, GH did not produce a measurable increase in either strength or exercise capacity. And the subjects who got GH were more likely to retain fluid and experience fatigue than were the volunteers who got the placebo.
If you were a jock in school or college, you're likely to wince at the memory of your coach barking "no pain, no gain" to spur you on. Today, athletes who use illegal performance-enhancing drugs risk the pain of disqualification without proof of gain.
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An Anti-Aging Andidote?
As men age, GH levels fall. In addition, muscle mass declines and body fat increases. That's where the theory comes from that injecting GH will stop these effects of aging.
Similar claims have been made for other hormones that decline with age, such as testosterone and DHEA in men, and estrogen in women. Research shows that post-menopausal estrogen therapy does more harm than good in some older women. And there is no solid evidence that testosterone and DHEA are safe and effective for healthy older men. But that has not stopped the growth of "anti-aging" and "regenerative medicine" clinics and websites.
Many practitioners offer expensive injections of growth hormone, even though using GH for anti-aging, body building, and athletic enhancement is illegal in the U.S. According to one estimate, however, 20,000 to 30,000 Americans used GH as "anti-aging" therapy in 2004 alone.
To evaluate the safety and efficacy of GH in healthy older people, a team of researchers reviewed 31 high-quality studies that were completed after 1989. They evaluated the data from 220 subjects who received GH and 227 control subjects who did not get the hormone. Two-thirds of the subjects were men; their average age was 69 and the typical volunteer was overweight but not obese.
The dosages of GH varied considerably and the therapy lasted from 2 to 52 weeks. Here's what the researchers found:
- The hormone boosted levels of IGF-1, which reflects the level of GH, by 88%.
- The treated individuals gained an average of 4.7 pounds of lean body mass, and shed a similar amount of body fat compared with the subjects who did not get GH.
- There was a slight drop in total cholesterol levels with GH, but no significant change in LDL ("bad") cholesterol, HDL ("good") cholesterol, triglycerides, aerobic capacity, bone density, or fasting blood sugar and insulin levels.
- Subjects who received GH had a high rate of side effects including fluid retention, joint pain, breast enlargement and carpal tunnel syndrome.
- The studies were too short to detect any change in the risk of cancer, but other research suggests that high IGF-1 levels may be linked to an increased risk of cancer in general and prostate cancer in particular.
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Beat the Clock
Although more study is needed, GH does not appear to be either safe or effective for young athletes or healthy older men. But that doesn't mean you have to sit back and let Father Time have his way with you.
You can slow the tick of the clock and reduce your risk of many chronic diseases with the time-tested combination of diet and exercise. Both can enhance your vigor and enjoyment of life.
- Aim for a moderate protein intake of about .36 grams per pound of body weight; even big men don't need more than 65 grams (about 2 ¼ ounces) a day, though athletes and men recovering from illnesses or surgery might do well with an extra 20 grams or so.
- Include at least 30 minutes of moderate exercise a day, such as walking; strength train two or three times a week to build muscle mass and strength.
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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.