Growth hormone, athletic performance, and agingA closed meeting of 55 international scientists with expertise in GH, including pediatric and adult endocrinologists, basic scientists, regulatory scientists, and participants from the human growth hormone research industry. Current literature was reviewed for gaps in knowledge. Expert opinion was used to suggest studies required to address potential safety and efficacy issues. Following plenary presentations summarizing the literature, breakout groups discussed questions framed by the planning committee. Attendees reconvened after each breakout session to share group reports. A writing team compiled the breakout session reports into a draft document that was discussed and revised in an open researchh on the concluding day. This was edited further and human growth hormone research circulated to attendees from academic institutions for review dball over shoulder the meeting.
The Growth Hormone Research Society
In , the Spanish explorer Juan Ponce de Len arrived in Florida to search for the fountain of youth. If he got any benefit from his quest, it was due to the exercise involved in the search. Few men today believe in miraculous waters, but many, it seems, believe in the syringe of youth. Instead of drinking rejuvenating waters, they inject human growth hormone to slow the tick of the clock.
Some are motivated by the claims of the "anti-aging" movement, others by the examples of young athletes seeking a competitive edge. Like Ponce de Len, the athletes still get the benefit of exercise, while older men may use growth hormone shots as a substitute for working out. But will growth hormone boost performance or slow aging?
And is it safe? Growth hormone GH is a small protein that is made by the pituitary gland and secreted into the bloodstream. GH production is controlled by a complex set of hormones produced in the hypothalamus of the brain and in the intestinal tract and pancreas. The pituitary puts out GH in bursts; levels rise following exercise, trauma, and sleep. Under normal conditions, more GH is produced at night than during the day. This physiology is complex, but at a minimum, it tells us that sporadic blood tests to measure GH levels are meaningless since high and low levels alternate throughout the day.
But scientists who carefully measure overall GH production report that it rises during childhood, peaks during puberty, and declines from middle age onward.
GH acts on many tissues throughout the body. In children and adolescents, it stimulates the growth of bone and cartilage. In people of all ages, GH boosts protein production, promotes the utilization of fat, interferes with the action of insulin, and raises blood sugar levels. GH also raises levels of insulin-like growth factor-1 IGF GH is available as a prescription drug that is administered by injection.
GH is indicated for children with GH deficiency and others with very short stature. It is also approved to treat adult GH deficiency — an uncommon condition that almost always develops in conjunction with major problems afflicting the hypothalamus, pituitary gland, or both.
The diagnosis of adult GH deficiency depends on special tests that stimulate GH production; simple blood tests are useless at best, misleading at worst. Adults with bona fide GH deficiencies benefit from GH injections.
They enjoy protection from fractures, increased muscle mass, improved exercise capacity and energy, and a reduced risk of future heart disease. But there is a price to pay. Adults who are GH deficient get larger muscles, more energy, and improved exercise capacity from replacement therapy.
Athletes work hard to build their muscles and enhance performance. Some also turn to GH. It's not an isolated problem. Competitive athletes who abuse GH risk disqualification and disgrace. What do they gain in return?
And do they also risk their health? Because GH use is banned and athletic performance depends on so many physical, psychological, and competitive factors, scientists have been unable to evaluate GH on the field. But they can conduct randomized clinical trials that administer GH or a placebo to healthy young athletes and then measure body composition, strength, and exercise capacity in the lab.
A team of researchers from California conducted a detailed review of 44 high-quality studies of growth hormone in athletes. A total of volunteers received GH injections, while received placebo. After receiving daily injections for an average of 20 days, the subjects who received GH increased their lean body mass which reflects muscle mass but can also include fluid mass by an average of 4. That's a big gain — but it did not translate into improved performance.
In fact, GH did not produce measurable increases 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 high 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. Among its many biological effects, GH promotes an increase in muscle mass and a decrease in body fat.
As men age, GH levels fall. During the same time span, muscle mass declines and body fat increases. And so, the theory goes, the way to arrest these effects of aging is to inject GH.
Similar claims have been made for other hormones that decline with age, including testosterone and dehydroepiandrosterone DHEA in men, and estrogen in women. Research shows that estrogen replacement does more harm than good in 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 Web sites. Expensive injections of growth hormone are offered by many practitioners, even though the FDA has not approved the use of GH for anti-aging, body building, or athletic enhancement, and the marketing or distribution of the hormone for any of these purposes is illegal in the U.
According to one estimate, 20, to 30, Americans used GH as "anti-aging" therapy in alone; according to another, , people received GH without a valid prescription in 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 Each of the studies was small, but together they evaluated subjects who received GH and 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 dosage of GH varied considerably, and the duration of therapy ranged from two to 52 weeks. As compared to the subjects who did not get GH, the treated individuals gained an average of 4.
There was a slight drop in total cholesterol levels, but no significant changes in LDL "bad" cholesterol, HDL "good" cholesterol, triglycerides, aerobic capacity, bone density, or fasting blood sugar and insulin levels. But GH recipients experienced 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 an increased risk of cancer in general and prostate cancer in particular. And while 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 peck away at you. Instead, use the time-tested combination of diet and exercise. Aim for a moderate protein intake of about.
Plan a balanced exercise regimen; aim for at least 30 minutes of moderate exercise, such as walking, a day, and be sure to add strength training two to three times a week to build muscle mass and strength. You'll reduce your risk of many chronic illnesses, enhance your vigor and enjoyment of life, and — it's true — slow the tick of the clock.
Harvard Men's Health Watch.