July 25, 2002 -- Use of human growth hormone may be linked to cancer, British researchers report. It's likely not a problem for people who need the hormone for medical reasons. But those who take costly "anti-aging" growth hormones may risk more than their money.
The study in the July 27 issue of The Lancet looks at nearly 2,000 British patients who, as children, were treated with human pituitary growth hormone. Use of this human-brain-derived product stopped in 1985 when it was linked to a fatal brain disease -- CJD, a variant of which is now called mad cow disease.
Newer, synthetic forms of human growth hormone (hGH) don't have this problem. But Anthony J. Swerdlow, MD, PhD, and colleagues at England's Institute of Cancer Research worry that hGH may have other risks. They took a hard look at the lifetime medical records of the children -- now adults -- who took the hormone between 1959 and 1985.
The alarming finding: taking the old form of hGH significantly increased risk of cancer, especially colon cancer and Hodgkin's disease. Swerdlow says there is no reason for people with hormone deficiencies to stop taking hGH. It's impossible to draw conclusions from so few cases of cancer among so few people. But he says the need for more study is urgent -- especially as more and more people are taking hGH for more and more reasons.
"Our data applies to childhood treatment and not to adults," Swerdlow tells WebMD. "It is up to people and their doctors to make a decision on what to do. There are no data on healthy people taking growth hormone for long periods. But you would have to say that it is growth hormone and there might be similarities."
The fastest-growing use of hGH today is among healthy adults who take it as part of popular "anti-aging" programs. The body makes less and less growth hormone as a person ages. Anti-aging programs use hGH to give aging men and women the growth hormone levels of a much younger person.
"Almost half of growth hormone sold today is not for hormone deficiency -- it is for people who want to feel young again," Michael Pollak, MD, tells WebMD. "They say, 'This may help me and it has no risks.' This study says, 'Nope, growth hormone at age-inappropriate levels may be dangerous.'"
Pollak, director of the cancer prevention unit at Canada's McGill University in Montreal, is co-author of an editorial published alongside the Swerdlow study. The editorial supports Swerdlow's worry that hGH has a role in cancer -- especially colon cancer.
One effect of hGH is to raise blood levels of a substance called insulin-like growth factor type I (IGF-I). Animal studies show that high levels of IGF-I cause cancer. Colon-cancer cells grow faster when exposed to IGF-I. People with a disease called acromegaly have too much IGF-1 in their blood -- and they are at high risk of colon cancer.
"The fact that these hormone levels decline with age may be an appropriate balance," Pollak says. "You may be subjecting yourself to risks if you keep these levels high."
In an October 2000 interview with WebMD, Stanley Slater, MD, discussed the fad of using hGH to slow the aging process. Slater is associate director for geriatrics at the U.S. National Institute on Aging.
"When people ask, I tell them not to take growth hormone but to wait until it is clinically established to be useful," Slater says. "There is no clinical evidence of it causing tumors to grow faster, but on biological grounds there is some suspicion. If you give someone growth hormone for 30 years, nobody knows what will happen."