Insulin-like growth factor 1 (IGF-1)

Insulin-like growth factor I (IGF-1) is one of a group of peptides including IGF-2 and IGF binding proteins, whose principal role is to coordinate growth and metabolism. IGF-I is highly dependent on growth hormone and has potent growth promoting activity. It is primarily synthesized in the liver, and then transported in plasma by IGF-binding proteins such as IGFBP-2 and IGFBP-3, These binding proteins are responsible for the relatively high concentration of IGF-1 in plasma and act to minimize plasma concentration fluctuations. IGF-1 measurements are useful in the diagnosis of growth disorders as an adjunct to assessment of growth hormone secretion. Patients with active acromegaly consistently have elevated IGF-1 concentrations. Serum IGF-1 also seems to correlate with disease status significantly better than growth hormone and may therefore be a superior means to indicate improvement following therapy.

In addition, IGF-1 measurement is useful in the investigation of short stature in children. If measured in conjunction with growth hormone during a stimulation test, it may assist in establishing the cause of retarded growth. A low IGF-1 value cannot be taken as proof of growth hormone deficiency since it is also compatible with nutritional deficiency, chronic illness and hypothyroidism.