DEAR DOCTOR K >> A friend of mine who is in her 70s is getting growth hormone shots. She says it fights aging. I'm dubious that anything can fight aging and worry about side effects. Am I just old-fashioned?
DEAR READER >> Well, you certainly are right to ask these questions. If there was a treatment that could slow aging and was risk-free, I guess we'd all take it.
Growth hormone (GH) is a protein produced by the pituitary gland in the brain. It gets its name from the fact that it is important in stimulating growth during childhood. Children born with a growth hormone deficiency are destined to be very short unless they are treated with growth hormone early in life.
What about using GH in aging adults? First of all, there is absolutely no evidence that taking GH supplements will lengthen a person's life. However, it does appear to have some beneficial 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.
To evaluate the safety and effectiveness of GH in healthy older people, a team of researchers reviewed 31 high-quality studies. Together, these studies evaluated 220 people who received GH and 227 people who did not. Two-thirds of the subjects were men; their average age was 69. The dosage of GH varied, as did the duration of therapy.
As compared to the subjects who did not get GH, the treated individuals gained an average of 4.6 pounds of lean body mass and shed a similar amount of body fat. 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. Sounds good, so far.
But here comes the bad news. People who used GH experienced a high rate of side effects. These included fluid retention, joint pain, breast enlargement and carpal tunnel syndrome.
A bigger concern is cancer. In laboratory studies, GH promotes the multiplication of cancer cells. Some epidemiological studies have found that people with naturally high levels of GH have higher rates of cancer. These studies by no means prove that taking GH supplements raises a person's risk of cancer, but it's plausible that they might.
So I don't recommend taking GH supplements to fight aging. But there is a truly magical treatment that does slow aging in all parts of the body, including the brain — and it needn't cause side effects. If you're regular readers of this column, you've probably guessed the name of the magical treatment: regular exercise.
Dr. Komaroff is a physician and professor at Harvard Medical School.