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Test Name:
Insulin-Like Growth Factor I
- SBMF No:
30053 - Performance Lab Name:
Manual Lab - Test Mnemonic:
IGF-1 - ABN:
Not required - CPT Code:
84305 - Also Known As:
IGF-1; IGF-I; Somatomedin C - Spec Collect:
Gold top (SST) or Red top (serum) tube - Spec Process:
Separate serum from cells ASAP or within one hour of collection. Transfer 1 mL serum or plasma to a separate plastic tube and freeze. (Min: 0.5 mL) - Spec Store Transport:
Frozen - Spec Stability:
24 hours refrigerated (2-8°C)
1 year frozen (-20°C)– Do not use frost-free units that undergo repeated freeze/thaw cycles - Spec Reject:
Tissue or urine. Grossly hemolyzed or lipemic specimens. - Methodology:
Quantitative Chemiluminescent Immunoassay (ChLIA) - Use:
Used in the diagnosis of growth disorders; measurements of IGF-I are a useful adjunct to assessment of growth hormone (GH) secretion - Clinical Significance:
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.
- Reference Range:
By report - Additional Test Info:
- Day Run:
Thu - Time Run:
8:00 am - Time Reported:
5:00 pm - Test Type:
HORMONE
