Aging: Can Hormones Prevent Aging? (cont.)

Growth Hormone

Human growth hormone (hGH) is made by the pituitary gland, a pea-sized structure located at the base of the brain, and is important for normal development and maintenance of tissues and organs. It is especially important for normal growth in children.

Studies have shown that injections of supplemental hGH are helpful to certain people. Sometimes children are unusually short because their bodies do not make enough hGH. When they receive injections of this hormone, their growth improves. Young adults who have no pituitary gland (because of surgery for a pituitary tumor, for example) cannot make the hormone and they become obese. When they are given hGH, they lose weight.

Like some other hormones, blood levels of hGH often decrease as people age, but this may not necessarily be bad. At least one epidemiological study, for instance, suggests that people who have high levels of hGH are more apt to die at younger ages than those with lower levels of the hormone. Studies of animals with genetic disorders that suppress growth hormone production and secretion also suggest that reduced growth hormone secretion may prolong survival in some species.

Although there is no conclusive evidence that hGH can prevent aging, some people spend a great deal of money on supplements. These supplements are claimed, by some, to increase muscle, decrease fat, and to boost an individual's stamina and sense of well being. Shots-the only proven way of getting the body to make use of supplemental hGH-can cost more than $15,000 a year. They are available only by prescription and should be given by a doctor. In any case, people in search of the "fountain of youth" may have a hard time finding a doctor who will give them shots of hGH because so little is known about the long-term risks and benefits of this controversial treatment. Some dietary supplements, known as human growth hormone releasers, are marketed as a low-cost alternative to hGH shots. But claims that these over-the-counter products retard the aging process are unsubstantiated.

While some studies have shown that supplemental hGH does increase muscle mass, it seems to have little impact on muscle strength or function. Scientists are continuing to study hGH, but they are watching their study participants very carefully because side effects can be serious in older adults. These include diabetes and pooling of fluid in the skin and other tissues, which may lead to high blood pressure and heart failure. Joint pain and carpal tunnel syndrome also may occur. A recent report that treatment of children with human pituitary growth hormone increases the risk of subsequent cancer is a cause for concern. Further studies on this issue are needed. Whether older people treated with hGH for extended periods have an increased risk of cancer is unknown.

For now, there is no convincing evidence hGH supplements will improve the health of those who do not suffer a profound deficiency of this hormone.

Melatonin

This hormone is made by the pineal gland, a structure in the brain. Contrary to the claims of some, secretion of melatonin does not necessarily decrease with age. Instead, a number of factors, including light and many common medications, can affect melatonin secretion in people of any age.

Melatonin supplements can be bought without a prescription. Some people claim that melatonin is an anti-aging remedy, a sleep remedy, and an anti-oxidant (antioxidants protect against "free radicals," naturally occurring oxygen-related molecules that cause damage to the body). Early test-tube studies suggested that, in large doses, melatonin might be effective against free radicals. However, cells produce antioxidants naturally, and in test-tube experiments, cells reduce the amount they make when they are exposed to additional antioxidants.

Claims that melatonin can slow or reverse aging are very far from proven. Studies of melatonin have been much too limited to support these claims and have focused on animals, not people.

Research on sleep shows that melatonin does play a role in our daily sleep/wake cycle, and that supplements, in amounts ranging from 0.1 to 0.5 milligrams, can improve sleep in some cases. If melatonin is taken at the wrong time, though, it can disrupt the sleep/wake cycle. Other side effects may include confusion, drowsiness, and headache the next morning. Animal studies suggest that melatonin may cause some blood vessels to constrict, a condition that could be dangerous for people with high blood pressure or other cardiovascular problems.

These side effects are important to keep in mind since the dose of melatonin usually sold in stores-3 milligrams-can result in amounts in the blood from 10 to 40 times higher than normal. What long-term effects such high concentrations of melatonin may have on the body are still unknown. Until researchers find out more, caution is advised.

Testosterone

Ask an average man about testosterone, and he might tell you that this hormone helps transform a boy into a man. Or, he might tell that you that it has "something" to do with sex drive. Or, if he has read news stories in recent years, he might mention "male menopause," a condition supposedly caused by diminishing testosterone levels in aging men. In reality, there is scant evidence that this controversial condition, also known as "andropause" or "viropause," exists.