INSULIN LIKE GROWTH FACTOR 1
- INSULIN LIKE GROWTH FACTOR 1
- Start Date
- Expiration Date
- IGF; Somatomedin; IGF-1
- CPT Codes
- Reference Test
- Transport Info
Centrifuge and immediately transfer serum to separate plastic tube
- Fasting Required?
- Patient Instructions
- Reference Range
Chemiluminescent Immunoassay (ChLIA)
Used in the diagnosis of growth disorders; measurements of IGF-I are a useful adjunct to assessment of growth hormone (GH) secretion
The insulin-like growth factors (IGFs), also referred to as the somatomedins, are a family of peptides whose serum concentrations are regulated principally by growth hormone (GH) and nutritional intake. In humans, IGF peptides have been identified as IGF-I (Somatomedin-C) and IGF-II. IGF-I has a molecular weight of 7,649 Daltons and PI (Isoelectric Point) of 8.2-8.7. It contains 70 amino acid residues in a single chain with 3 disulfide bridges. It is highly dependent on growth hormone and has potent growth-promoting activity in many systems. In serum or plasma, the IGFs are bound to larger proteins.
In the diagnosis of growth disorders, measurements of IGF-I are a useful adjunct to assessment of growth hormone (GH) secretion. A normal plasma or serum IGF-I concentration is strong evidence against GH deficiency, with exceptions being some GH deficient children with craniopharyngiomas and adults who have a prolactin secreting tumor accompanied with GH deficiency and prolactin excess. A low IGF-I value cannot be taken as proof of GH deficiency and requires additional testing to determine whether GH secretion is subnormal. A low IGF-I in a short child is compatible with GH deficiency, nutritional deficiency, chronic illness and/or hypothyroidism.
Patients with active acromegaly almost uniformly have elevated IGF-I values. IGF-I concentrations seem to correlate with disease significantly better than GH, and may provide an indication of improvement after therapy. Currently, the most readily apparent use for serum measurements of IGF-I are for the determination of GH deficiency or GH excess. Another potential use includes the assessment of change in nutritional status. Investigators should find the test useful in studying the effects of disease in serum concentrations of this peptide.