Diagnosis and Treatment of Adult Growth Hormone Deficiency
Overview
Adult Growth Hormone Deficiency (AGHD) is characterized by diminished growth hormone (GH) secretion by the pituitary gland. This can be have many causes, including the presence of a pituitary tumor, other growths/disorders in the pituitary or hypothalamic area, history of surgery or radiation therapy to the pituitary area or base of skull, or head trauma. In these situations, reduced GH secretion in children leads to short stature. In adults, the clinical syndrome includes:
- Altered body composition (increased fat mass, decreased lean body mass)
- Decreased muscle strength
- Altered lipid profile
- Decreased bone mineral density
- Diminished quality of life, characterized by low energy level, increased emotional lability and irritability, and increased social isolation
- Enhanced cardiovascular risk
- In children: short stature
GH appears to be one of the first hormones to be lost in patients with pituitary tumors and nearly all patients with two or more pituitary deficiencies also lack GH.
Diagnosis
Because GH is released in pulses, random blood measurement of GH is not a reliable indicator of GH status. In most instances, a provocative test (i.e., a stimulation test) is necessary to document GH deficiency. The insulin tolerance test (ITT), arginine test, and GH-releasing hormone (GHRH) test are some examples of commonly used stimulation tests. These tests take approximately 2 hours and are done on an outpatient basis. Insulin-like growth factor-1 (IGF-1) is a hormone produced by the liver (and peripheral tissues) in response to circulating GH. IGF-1 is a general marker of GH status, and a low random serum IGF-1 value may reflect the presence of AGHD.
Treatment
Recombinant GH (rhGH) is administered by once daily subcutaneous injections in a fashion very similar to the way in which a diabetic patient self-administers insulin. Patients are often started on a low initial dose, with dose increases based on clinical response and serum IGF-1 levels adjusted to the mid-normal range for age and gender. GH therapy has been shown to improve lean body mass, bone density, exercise tolerance, personal productivity and quality of life. The most common side effects are fluid retention and muscle/joint aches. These side effects are largely dose related, and these symptoms can be minimized by starting with a low initial dose and/or dose reductions