And It's About Time There Was Some Support For Cushing's!
THIS INFORMATION WAS DEVELOPED BY DAVID COOK, M.D. IT IS NOT INTENDED TO SUBSTITUTE FOR A FULL AND FRANK CONSULTATION WITH QUALIFIED MEDICAL PERSONNEL, WHICH IS THE PRIMARY MEANS FOR A PATIENT TO OBTAIN CARE AND TREATMENT. THE INFORMATION WAS BELIEVED TO BE CURRENT ON NOVEMBER 5, 1998 AND WITH THE LAPSE OF TIME, CERTAIN OF THIS MATERIAL WILL BE OUTDATED.
by David Cook, M.D.
Adults need growth hormone too!
Growth hormone (GH) is a protein hormone made by the pituitary, a hormone producing gland located at the base of the skull. The pituitary gland not only produces GH, but releases (secretes) GH into the bloodstream. After entering the bloodstream, GH attaches to certain tissues, especially bones, and results in height increase in children. Damage to the pituitary gland in children results in low GH secretion in children, resulting in poor growth and resultant short stature. GH can be given to children to restore their normal growth and development.
Over the last ten years, it has been discovered that adults need GH too. Like children, adults can be given this hormone if deficient. The approval by the FDA to give GH to deficient adults has been in place for the last two years. Since adults have already achieved their genetically determined height, loss of GH does not impact height, but it does affect the body in many other ways. If adults have a deficiency of GH, major changes to the composition of the body results. These changes include loss of muscle, accumulation of fat, especially in the abdomen, and a decrease in the density (but not the length) of bones. Because GH is also necessary for normal brain function, adults without this hormone have psychological changes in addition. This article will focus on describing the GH deficiency syndrome as it applies to adults, and how it is currently diagnosed and treated.
There are three components to the adult GH deficiency syndrome. These are body composition changes, blood lipid (cholesterol and fat) changes, and psychological changes. Because GH maintains muscle and fat, loss of this hormone results in a decrease in muscle and in an accumulation of fat. The decrease in muscle translates to poor muscle function and decreased exercise capacity. The increase in fat occurs under the skin, but also in the abdomen or, more specifically, inside the abdomen. This location is referred to as visceral fat. Medical science has discovered that visceral fat accumulation is especially dangerous because it is associated with an increase in the aging of blood vessels, referred to as atherosclerosis. The blood lipid changes reflect the fat deposit changes and are all in the wrong direction. More specifically, there is an increase in the "bad" cholesterol ("LDL cholesterol") and a decrease in the "good" cholesterol ("HDL cholesterol"). There is also an increase in the blood triglycerides, another circulating fat, which is associated with blood vessel aging.
The psychological changes associated with GH deficiency have been extensively studied. Patients who develop GH deficiency seem to lose energy. Loss of energy is often the guiding symptom which prompts further investigation. Many individuals with pituitary disease, especially those with other hormone deficiencies, realize that something is missing. Frequently, it turns out to be a deficiency of GH. Individuals with this problem, or their spouses, also notice a loss of interest in their usual hobbies or activities. A decrease in sociability referred to as social isolation is another symptom. Patients suffering with this symptom do not like to go out and meet with their friends or social acquaintances. Patients may also develop mild depression or decrease in sexual function.
GH deficiency in adults occurs because of some type of injury to the pituitary gland. Injury usually can occur because of the presence of a pituitary tumor, or pituitary surgery or pituitary irradiation. It can also be caused by trauma to the gland or, very rarely, inflammation. The cause is usually quite obvious to the endocrinologist physician, who will consider the diagnosis of GH deficiency in patients with known pituitary damage. Although GH circulates in blood, it disappears rapidly from the bloodstream and enters into the tissues. Because of this, GH is commonly undetectable in normal individuals as well as in GH deficient patients. A blood GH level taken randomly, in other words, is usually low. For this reason, endocrinologists need to find another way to prove deficiency of this hormone. This is done by checking to see if stimulating the pituitary releases GH. There are various ways to stimulate the pituitary to release GH (called "GH stimulation tests"). If your physician thinks you may be GH deficient, he or she will usually pick one of the standard tests. The testing is done in the outpatient setting and usually takes about two to three hours. You may be instructed not to eat prior to the test. This type of stimulation testing is not only necessary for medical diagnosis, but often for insurance purposes.
Once a physician has proven GH deficiency, he or she will begin the patient on a small dose of GH and slowly raise the dose until a final maintenance dose is reached. The hormone is given daily by injection. The hormone is given by the patient or a member of the family. Small needles and syringes are used. The physician will see the patient at four to eight week intervals to ask how the patient is doing and to obtain a blood test which can help determine the correct dose. This test is the insulin-like growth factor test ("IGF-1 test"). It is a single blood test which reflects the amount of GH administered, although it is not GH itself. IGF-1 values which are low prompt a larger dose or growth hormone is needed; values which are too high prompt a lower dose. Once a final dose is established, the blood test and office visits will continue approximately every 4 to 6 months. The symptoms of GH excess include muscle or joint pain, retention of fluid (called edema) and carpal tunnel, which consists of pain and/or numbness in the hands. These symptoms, if severe, will also help determine the dose.
There are other ways the physician will monitor GH therapy. If the patient has a pituitary tumor, an MRI will be performed before therapy begins and usually every year thereafter. It is not known whether or not GH can stimulate the growth of residual tumors. The endocrinologist physician will decide when and how often this should be performed. The physician will often elect to monitor blood cholesterol and bone density. Successful therapy is associated with an increase in the density of bones and an improvement in blood cholesterol profile.
Deficiency of GH in the adult has been recently described. It has recently been approved as acceptable therapy by the FDA. Most insurance will cover the cost of this medication, which is quite expensive. Improvement in most of the symptoms and body composition changes induced by this deficiency change for the better with successful therapy. GH replacement therapy for GH deficient adults is considered lifelong therapy.