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Over the past few years, hundreds of clinics have sprung up, providing human growth hormone to thousands of elderly people looking for a fountain of youth. Athletes, would-be athletes and bodybuilders also take it, often in huge amounts, hoping to build muscle. But there has been almost no objective evidence on whether it works.
Now, in one of the largest and most careful studies so far of human growth hormone in healthy older people, researchers find that it can markedly transform older people's bodies. The effects were potent. Those who took the drug gained lean body mass, much of which is likely to be muscle, and lost fat as if they had been working out in a gym, lifting weights and doing aerobic exercise. Some men gained 10 pounds of lean body mass and lost an equivalent amount of fat. Yet the subjects, who ranged in age from their mid-60's to their late 80's, were sedentary and did not exercise or change their diets.
But the investigators caution that these gains were accompanied by serious adverse side effects in nearly half the subjects, who developed pre-diabetes or diabetes, aching joints and swollen tissues.
The findings, the scientists said, give them hope, but much work remains. The study lasted just six months, and there is concern that growth hormone may have terrible long-term effects — in animals it can actually speed aging and reduce the life span, and scientists fear it could promote the growth of cancers. In people, growth hormone can cause arthritis, and some experts worry that the joint pains that plagued many in the study might lead to arthritis if the drug were continued.
"This is a fascinating area for further research," said Dr. Marc Blackman, a director of the new study, which is being published today in The Journal of the American Medical Association. But, Dr. Blackman cautioned, "we don't think this is ready for prime time yet."
Growth hormone therapy should not be used outside a controlled clinical trial, said Dr. Blackman, who directs the laboratory of clinical investigation at the National Center for Complementary and Alternative Medicine.
The researchers were asking whether growth hormone and, possibly, sex hormones might be a key to the debilitating changes that occur with aging. Starting about age 30, growth hormone levels start to decline. By age 60, people can have half as much as they did at 30. Testosterone, in men, declines, too, and, in women, estrogen levels plummet after menopause. The hypothesis was that the effects of aging — shriveling muscles, thinning bones, increased body fat, especially in the abdomen, a loss of energy and enthusiasm, might be linked to hormone deficiencies, and, in particular, a lack of growth hormone.
People who lack growth hormone — for example, patients with a genetic defect or a tumor of the pituitary gland that prevents the hormone from being made — have all these signs and symptoms of aging, and they are reversed when they take growth hormone injections.
Sex hormones may also play a role, Dr. Blackman said. "Sex steroids stimulate the growth hormone system," he said. "At least in younger people, when one is awry, the other one goes down."
In their study, the researchers tried to recreate in older people the hormone levels of a 20- or 30-year-old. They recruited 57 women and 74 men, with ages from 65 to 88, giving them hormones or dummy medications.
The most striking results were in the men who took both growth hormone and testosterone. They gained almost 10 pounds of lean body mass and lost a corresponding amount of fat. They also increased their cardiovascular endurance, a measure of their ability to exercise. Men who took growth hormone alone gained seven pounds of lean body mass and lost a similar amount of fat but their endurance did not change.
The women who took growth hormone, with or without estrogen and progesterone, gained a few pounds of lean body mass and lost five pounds of fat. In both men and women, sex hormones alone did not significantly change their body composition. Growth hormone appeared to be the major factor.
The side effects, however, were serious, afflicting 24 percent to 46 percent of the men and women taking growth hormone and including swollen feet and ankles, joint pain and carpal tunnel syndrome, which is caused by a swelling of a tendon sheath over a nerve in the wrist. It, and the joint pain, might be caused by the drug's tendency to increase water retention, Dr. Blackman said.
But Dr. S. Mitchell Harman, an author of the new study and director of the Kronos Longevity Research Institute, a nonprofit center that does research on aging, said it might be a result of growth hormone's effects in increasing tissue growth.
In addition, half the men who took growth hormone also had impaired abilities to use glucose, developing either diabetes or a prediabetic condition. But all these adverse effects disappeared when the study ended and the men and women stopped using the drugs.
Participants in the study did not grow stronger, even though they gained muscle, but it is possible that that might change if the treatment continues longer, said Dr. Harman, who also helped direct the study. Dr. Harman noted that when the hormone was given to people with rare medical conditions who lacked it, "you see very little increase in muscle strength until a year."
Dr. Blackman was cautious. "I personally believe these data are quite exciting," he said. "But there are two issues that are the bottom line. One is that we are uncertain about the possible effects and their functional relevance — getting out of a car, being able to bathe. The other is that there needs to be a lot more research with larger numbers of people and a reduction of these adverse effects."
Dr. Michael Thorner, chairman of the department of medicine at the University of Virginia School of Medicine, said the recent fall from grace of hormone therapy in menopause should give people pause. "If you just advocate that growth hormone be used because it might help," Dr. Thorner said, "the next thing you know, the whole world is on it. I think in medicine one should tailor therapies based on evidence."
The marketing of growth hormone took off in 1990 with the publication of one preliminary study of 12 men, indicating that they had lost fat and gained muscle. Soon afterward, researchers said, anti-aging clinics sprang up to offer the drug, at a cost of $1,000 or more a month, to people looking for a way to turn back the clock.
Growth hormone, made by Genentech, Eli Lilly & Company and others, is approved for use by children and adults with rare medical conditions that make them lack it. But once a drug is on the market, doctors can prescribe it at their discretion.
In just the last four years, according to IMS Health, a company that tracks drug sales, prescriptions for growth hormone made by Genentech and Eli Lilly have more than tripled, rising to 21,000 in 2001 from 6,000 in 1997.
While some prescriptions are for legitimate uses, medical experts say, many others are not. For example, growth hormone is also used by athletes and bodybuilders, with magazines directed toward these groups advertising its availability. The current issue of Men's Fitness, for example, has three ads for growth hormone, providing telephone numbers that people can call for a list of doctors who will prescribe the drug.
"There are plenty of doctors who will prescribe it," said Dr. Harman said. "It's a tremendous scam."
Injections of human growth hormone, which have become increasingly popular as a virtual "fountain of youth," do reverse some of the common physical attributes of aging, a new federally sponsored study has found. But the shots also have potentially serious side effects, including increasing the risk of developing diabetes and carpal tunnel syndrome.
In the most extensive clinical trial so far of the hormone -- which is available at the many "anti-aging" clinics opening around retirement centers -- researchers concluded that the growth hormone treatment was not ready for widespread use, although it showed a "promising" ability to increase muscle and decrease fat in older people.
"There may be benefits to some older people in the use of growth hormone, but the safety is not established, and it should only be used in controlled trials," said Marc R. Blackman of the National Institutes of Health, who led the study. "This is not ready for prime time."
Human growth hormone has been approved by the Food and Drug Administration only to treat severe hormone deficiencies in children and adults, and for wasting in AIDS sufferers. But officials believe it is also being widely prescribed for older people who believe aggressive advertisements that promise the hormone will help keep them feeling and looking young. Black-market, and often counterfeit, growth hormone is used as well by athletes and body builders, FDA officials said.
Federal officials said there are no firm statistics on the overall use of the growth hormone, but some have estimated the number of older adults injecting the hormone to be 25,000 to 35,000. Some doctors involved in the business say the overall use exceeds 100,000 people when black-market sales are included. The black market consists of people getting the hormone without a prescription, or getting versions of the hormone made by counterfeiters. Yearly growth hormone sales have been estimated to be as high as $2 billion.
The new study, published in today's Journal of the American Medical Association, followed 131 men and women 65 to 88 years old. The subjects who were injected with the hormone developed significantly more muscle and lost significantly more fat than the placebo group, the researchers found. But 18 of the men on growth hormone developed diabetes or glucose intolerance, while only seven men who were not receiving the hormone developed those conditions. Carpal tunnel syndrome and swelling of limbs were also notable side effects.
Human growth hormone is made in the pituitary gland, a pea-sized structure located at the base of the brain, and is believed to be essential to the normal development of tissues and organs. The two sex hormones, testosterone and estrogen, work in combination with growth hormone to bring on puberty and maturation in teenagers.
Researchers such as Blackman believe a similar interaction occurs as men and women age, and that the level of both the growth hormone and sex hormones naturally decline. With the decline in growth and sex hormone levels, muscle mass tends to decrease and body fat increases. Some have also linked the hormone declines to decreased sexual drive and mood changes.
When growth hormone was initially developed as a medication, it was harvested from the pituitary glands of human cadavers. It has subsequently been produced by genetically engineered bacteria endowed with the gene for growth hormone.
In the new study, which was conducted by a team directed by the NIH's National Institute on Aging and Johns Hopkins University Medical Center, researchers found that both the positive and negative effects of growth hormone treatment were present in men and women. They also found that men given both growth hormone and testosterone -- but not growth hormone alone -- had significant improvements in their ability to exercise.
Despite the improvements in body composition regarding fat and muscle with the growth hormone, Blackman said that there was no measurable improvement in actual body strength. He said that could be explained by the relatively short duration of the trial.
S. Mitchell Harman, a study leader formerly with the NIH and now with the Kronos Institute for Longevity Research, warned that use of growth hormone should be seen as experimental research, rather than clinical therapy. "If you are taking it as an anti-aging miracle cure, you are fooling yourself," he said.
He called the business in growth hormone pills and sprays is "snake oil." He said the growth hormone molecule is too large to pass into the bloodstream unless it is injected.
Alan P. Mintz, head of Cenegenics Medical Institute in Las Vegas, one of the country's largest anti-aging centers, disputed the study findings. He said his patients have had great success and few side effects with growth hormone treatment, which he always gives in conjunction with broader hormone therapy.
He said that Cenegenics has about 4,000 patients, and about one-third spend $400 to $500 a month for growth hormone injections. He said the injections only bring patients up to a normal level of growth hormone, although he acknowledged there is dispute about what that is. He said his patients have seen improvements in body mass (the ratio of muscle to fat), in ability to exercise, to sleep and to enjoy sex.
The FDA has sent out at least two warning letters to companies advertising growth hormone in recent months, and a spokeswoman said misuse of the product was a clear concern for the agency.
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