Adult Growth Hormone Deficiency
Even after we stop growing, adults still need growth hormone. Growth hormone is a protein made by the pituitary gland and released into the blood.
Growth hormone plays a role in healthy muscle, how our bodies collect fat (especially around the stomach area), the ratio of high density to low density lipoproteins in our cholesterol levels and bone density. In addition, growth hormone is needed for normal brain function.
A person who has too little adult growth hormone will have symptoms that include:
- A higher level of body fat, especially around the waist
- Anxiety and depression
- Decreased sexual function and interest
- Feelings of being isolated from other people
- Greater sensitivity to heat and cold
- Less muscle (lean body mass)
- Less strength, stamina and ability to exercise without taking a rest
- Reduced bone density and a tendency to have more bone fractures as they get older
- Changes in the make up of the blood cholesterol.
People with adult growth hormone deficiency have higher than normal levels of low-density lipoproteins in comparison to their high density lipoproteins. They also tend to have higher triglyceride levels. (Triglycerides are another type of fat that circulates in the blood and contributes to blocked blood vessels.)
Causes and Risk Factors
A lack of growth hormone is usually caused by damage to the pituitary gland or the hypothalamus, a part of the brain that controls the pituitary gland. The damage may be due to a tumor; to surgery or radiation used to treat the tumor; or to problems with the blood supply to the pituitary gland.
In some cases, the lack of growth hormone is due to an injury to the pituitary gland.
A lack of growth hormone can appear either in childhood or in adulthood.
If a person has had surgery, an injury or a history of pituitary disorders, a doctor or endocrinologist (a specially trained physician who focuses on the health of hormone-secreting glands) will check for adult growth hormone deficiency. If there is a known disorder or problem with the pituitary gland, the doctor will probably order a magnetic resonance imaging (MRI) scan before any treatment is done. This allows the doctor to more accurately monitor how treatment is affecting the tumor.
Growth hormone in adults is absorbed quickly by tissues from the blood as it circulates. As a result of this, a blood test given to a healthy persons will show low levels of growth hormone. Endocrinologists instead check the pituitary gland's response when it is stimulated to produce growth hormone. These growth hormone stimulation tests are done in an outpatient setting and take about two to three hours. You will be asked not to eat before the test.
Once adult growth hormone deficiency has been confirmed, the doctor will prescribe daily doses of growth hormones. The hormone is injected into the patient's body; this can be done either by the patient or by a member of his or her family. Every four to eight weeks, the patient will return to the doctor for monitoring and a blood test to help the doctor decided if more hormone is needed or less.
If the person is getting too much growth hormone, he or she will have muscle or joint pain, swelling (fluid retention) and pain or numbness in the hands from carpal tunnel syndrome. If such symptoms appear, the doctor will lower the amount of growth hormone being given.
If the deficiency of growth hormone is due to a pituitary tumor, the doctor will monitor the tumor with MRIs every year. Currently, it is not known whether the growth hormone will cause tumors that remain in the pituitary gland to grow.
Finally, blood cholesterol and bone density will be monitored. With treatment of adult growth hormone deficiency, both of these measures should show signs of improvement.
Growth hormone therapy should not be given to people who have active cancer or tumors. It also should not be given to people who are seriously ill as a result of complications from open heart or abdominal surgery, who have multiple injuries from a major accident or who are have breathing problems. Taking growth hormone will not cause an adult to begin growing again.
Taking growth hormone can affect the way the body uses insulin, so it is important for anyone who has diabetes to keep their doctors informed and to be vigilant about monitoring blood sugar levels.