Growth Hormone, Insulin-Like Growth Hormone Factor I and Insulin-Like Growth Hormone Factor Binding Globulin (Growth Hormone, IGF-1 [Somatomedin C] and IGFBG-3)
IGF-1, also known as Somatomedin C, is a polypeptide hormone similar in structure to insulin. It is one of the main mediators of the actions of growth hormone in promoting muscular and skeletal growth. IGF-1 is itself a powerful anabolic hormone, and also prevents premature cell death. Because of its similarity to insulin, it also weakly activates the insulin receptor and therefore has insulin-like effects when present in large quantities.
Why test IGF-1?
Growth hormone (GH) stimulates IGF-1 production in the liver, and therefore IGF-1 levels reflect average daily levels of GH. Unlike GH, levels of IGF-1 do not fluctuate throughout the day. Measurement of Growth Hormone in 24 hour urine and IGF-1 in serum are currently are best methods available for screening and monitoring patients with Growth Hormone Deficiency. Liver production of IGF-1 is affected by nutritional factors, including protein deficiency and low insulin levels. Because of this, IGF-1 is a sensitive indicator of nutritional status for monitoring patients with eating disorders. Besides it can assess skeletal maturity (pubertal growth), help to reduce visceral obesity, thus helping to correct endocrine abnormalities and lessen cardio metabolic risk. A low IGF-1 level are also directly involved in the pathogenesis of insulin resistance, metabolic syndrome, and cardiovascular disease, type II diabetes, vascular protection and is now suggested as an important additional risk of cardiovascular disease risk.
Patients with Growth Hormone Deficiency suffer from:
- increased cardiovascular risk
- unfavorable lipid profile
- increased fibrinogen
- increased CRP ( inflammatory protein responsible for cardiovascular diseases)
- insulin resistance (diabetes)
- early arteriosclerosis
- endothelial dysfunction
- impaired left ventricular performance
- abnormal body composition
- increased level of homocycteine
- decreased microcirculation
- decreased function of immune system
- increased rate of cancer, tuberculosis, herpes, and shingles
- osteoporosis regardless of bone density
- slower wound and fracture healing
What is IGFBP-3?
IGFBP-3 is a serum transport protein. It causes IGF-1 to be bounded to itself and thus IGF-1 becomes inactive.