Below, Dr. Shlomo Melmed of Cedars-Sinai Health System talks about the role of growth hormone in the body and what can be done to set the level right again.
What does growth hormone do?
Growth hormone stimulates the bones and other organs to grow. It also regulates how cells utilize glucose and fat, and stimulates the liver to manufacture another hormone, called "insulin-like growth factor 1" or IGF1. IGF1 has a number of functions, and one is to stimulate bone growth.
What happens in the body when it doesn't have enough growth hormone?
If the deficiency occurs during infancy, childhood or adolescence, then that individual will not grow to the height at which he or she would have grown under normal circumstances. If, however, growth hormone deficiency occurs after the individual has completed his or her growth, then that individual will usually present with obesity, fat around the abdominal area, high lipid levels in the blood, low energy, decreased muscle mass and a general feeling of depression and isolation.
What happens if the body produces too much growth hormone?
If there is excess growth hormone prior to the end of the normal growth phase, then the individual will, in fact, continue to grow. So individuals who are seven feet tall or taller may have had excess growth hormone during their growth phase, which resulted in their long bones continuing to grow.
If there is excess growth hormone after the growth phase has ended, then bony overgrowth in the face, jaws, and skulls can occur. For example, patients will complain of increasing ring size or increasing shoe size, due to growth of those bones in the feet or in the fingers or, in fact, due to accumulation of water in the soft tissues. These are features of a condition we call "acromegaly," where there is generalized body overgrowth rather than increase in height.
What causes these imbalances in growth hormone production?
Excess growth hormone secretion is usually associated with a tumor-a benign tumor of the pituitary gland, which secretes excess amounts of growth hormone. Deficiency of growth hormone in children occurs either because of a hereditary or genetic condition in the pituitary gland which does not allow the pituitary to manufacture sufficient growth hormone or sufficiently effective growth hormone. Furthermore, any damage to the pituitary gland during childhood or after childhood can result in growth hormone deficiency. The most common cause of growth hormone deficiency in adults is a tumor in the pituitary or as a result of the surgery or radiation given to treat this tumor. Surgery or radiation to the head or neck for other conditions may also damage the pituitary and result in growth hormone deficiency.
How are people with excessive amounts of growth hormone treated?
Excess growth hormone secretion can be treated by surgery, radiation or medication. In surgery, a surgeon approaches the pituitary from the bottom of the skull. If the tumor is sufficiently small and circumscribed, then it can be removed and in most cases the problem will be cured and will not recur.
A second approach to treatment is to irradiate the pituitary tumor, which will slowly reduce the growth hormone over many years. Unfortunately, intolerable side effects can result from the radiation.
The third approach to treating growth hormone excess is to suppress the growth hormone secretion by means of medication. Several types of medications are available for this treatment. One group, called dopamine agonists, suppress the release of growth hormone. Somatostatin-like medicines are another group of drugs that mimic the body's normal somatostatin, a hormone secreted from the brain to regulate and suppress growth hormone secretion. So by injecting these somatostatin-like drugs, growth hormone secretion is suppressed.
How is growth hormone deficiency treated?
Growth hormone deficiency is very easily treated. It's treated by replacing growth hormone by injection either to a child or to an adult.
What are the conditions currently treated with growth hormone?
Growth hormone is approved for use in children with short stature due to multiple causes. It's approved for adults in whom normal growth hormone secretion is suppressed or absent. It's also approved for very specific wasting conditions, where muscle wasting occurs; for example, in the wasting that can occur with HIV infection.
Why is growth hormone useful in people with HIV/AIDS?
Because growth hormone is an anabolic agent, which means it improves muscle mass, strengthens muscles and decreases muscle wasting. So in conditions like HIV infection where there is a decreased muscle mass and a loss of body tissues, growth hormone acts as an anabolic agent and rebuilds that lost muscle tissue.
Is this why bodybuilders are using growth hormone, in addition to steroids, to build muscle bulk?
I suspect that bodybuilders are using growth hormone because they believe it to be a very powerful anabolic agent to improve muscle mass and muscle strength. But growth hormone is not approved for this use, and I would caution that the side effects of growth hormone in healthy individuals, in people who do not have growth hormone deficiencies, are such that it would not be advisable to take growth hormone without very careful physician supervision.
What are some of those side effects?
The most important side effects are enlarged jaw and facial features, mild diabetes, high blood pressure, fluid retention, and change in shoe size and ring size. Milder symptoms of growth hormone excess include fluid retention, muscle cramps, joint pain and arthritis.
Also, excess growth hormone can cause a condition of insulin resistance, so the individual may develop high blood sugar and diabetes, high levels of cholesterol and triglycerides in their blood, and obesity.
There has been a lot of talk in the popular press about the use of growth hormone as an antidote to aging. What's your response to this?
Again. This is a case of people using growth hormone who do not have growth hormone deficiencies. There are no proven studies to indicate that growth hormone will reverse any of the effects of aging, and the risks of side effects are like those for body builders.
I would rely on one's own physician for accurate information about what is currently known about growth hormone, specifically how it works. I would be very cautious in assuming that taking growth hormone will alleviate any of the features associated with aging.
