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Results of the Insulin-Like Growth Factor-1 assay are to be used in conjunction with other clinical and laboratory data to assist the clinician in the assessment of growth disorders.
Considerable differences exist between the currently available assays with respect to the results of IGF-1 measurements.
IGF-1 is a relatively small peptide (molecular weight 7647) that is tightly bound in serum to one of several high-affinity binding proteins.1 IGF-1 has approximately 50% sequence homology with proinsulin and has a number of biological activities similar to insulin. IGF-1 is a hormone that serves as the major effector of GH-stimulated somatic growth, as well as GH-independent anabolic responses in numerous tissues. IGF-1 has numerous growth-promoting effects, including mitogenic effects and the promotion of cartilage sulfation. Measurement of serum IGF-1 has been widely used in the diagnosis of disorders of GH secretion,2-6 management of disorders that lead to nutritional insufficiency or catabolism,7-9 and monitoring both GH and IGF-1 replacement therapy. IGF-I measurement may also have a role in the physiology of malignant disease.10,11
The IDS iSYS IGF-1 assay conforms to the recommendations outlined in the recently published consensus statement on the standardization and evaluation of IGF-1 assays.12 The assay is calibrated to the WHO recombinant reference standard 02/254 for IGF-1. Reference intervals were developed through a multicenter study with samples from 12 cohorts from the USA, Canada, and Europe.13 A total of 15,014 subjects were tested (6697 males and 8317 females), ranging in ages from 0 to 94 years. Results are reported in mass units with reference intervals reflecting the central 95% interval (2.5 to 97.5 percentiles). Z scores, which reflect the number of standard deviations a given result is above or below the age-adjusted mean, are reported along with the IGF-1 concentration.
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2. Clemmons DR. Clinical laboratory indices in the treatment of acromegaly. Clin Chim Acta. 2011 Feb 20; 412(5-6):403-409. PubMed 21075098
3. Melmed S, Colao A, Barkan A, et al. Guidelines for acromegaly management: an update. J Clin Endocrinol Metab. 2009 May; 94(5):1509-1517. PubMed 19208732
4. Katznelson L, Atkinson JL, Cook DM, et al. American Association of Clinical Endocrinologists medical guidelines for clinical practice for the diagnosis and treatment of acromegaly--2011 update. Endocr Pract. 2011 Jul-Aug; 17(Suppl 4):1-44. PubMed 21846616
5. Molitch ME, Clemmons DR, Malozowski S, et al. Evaluation and treatment of adult growth hormone deficiency: An Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jun; 96(6):1587-1609. PubMed 21602453
6. Cook DM, Yuen KC, Biller BM, Kemp SF, Vance ML; American Association of Clinical Endocrinologists. American Association of Clinical Endocrinologists medical guidelines for clinical practice for growth hormone use in growth hormone-deficient adults and transition patients−2009 update. Endocr Pract. 2009 Sep-Oct; 15(Suppl 2):1-29.
7. Friedrich N, Thuesen B, Jørgensen T, et al. The association between IGF-I and insulin resistance: A general population study in Danish adults. Diabetes Care. 2012 Apr; 35(4):768-773. PubMed 22374641
8. Kreitschmann-Andermahr I, Suárez P, Jennings R, Evers N, Brabant G. GH/IGF-I regulation in obesity--mechanisms and practical consequences in children and adults. Horm Res Peadiatr. 2010; 73(3):153-160. PubMed 20197666
9. Clemmons DR. Metabolic actions of insulin-like growth factor-I in normal physiology and diabetes. Endocrinol Metab Clin. North Am. 2012 Jun; 41(2):425-43, vii-viii. PubMed 22682639
10. Endogenous Hormones and Breast Cancer Collaborative Group, Key TJ, Appleby PN, et al Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies. Lancet Oncol. 2010 Jun; 11(6):530-542. PubMed 20472501
11. Khosravi J, Diamandi A, Mistry J, Scorilas A. Insulin-like growth factor I (IGF-I) and IGF-binding protein-3 in benign prostatic hyperplasia and prostate cancer. J Clin Endocrinol Metab. 2001 Feb; 86(2):694-699. PubMed 11158033
12. Clemmons DR. Consensus statement on the standardization and evaluation of growth hormone and insulin-like growth factor assays. Clin Chem. 2011 Apr; 57(4):555-559. PubMed 21285256
13. Bidlingmaier M, Friedrich N, Emeny RT et al. Reference intervals for insulin-like growth factor 1 (IGF-1) from birth to senescence: Results from a multicenter study using a new automated chemiluminescence IGF-1 immunoassay conforming to recent international recommendations. J Clin Endocrinolo Metab. 2014 May; 99(5):1712-1721. PubMed 24606072
