Insulin-like Growth Factor 1 (IGF-1)

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.

Malnutrition will cause low somatomedin-C levels in spite of normal amounts of circulating growth hormone. The Sm-C level does not distinguish pituitary dwarfism from constitutional delay of growth and development.2

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-1 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 In total, 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).

1. Holly JM, Perks CM. Insulin-like growth factor physiology: What we have learned from human studies. Endocrinol Metab Clin North Am. 2012 Jun; 41(2):249-263. PubMed 22682629

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, Merriam GR, Vance ML; Endocrine Society. 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. PubMed 20228036

7. Friedrich N, Thuesen B, Jrgensen 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):425-443, 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 J1, 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 Endocrinol Metab. 2014 May;99(5):1712-1721. PubMed 24606072

Daughaday WH, Hall K, Salmon WD Jr, Van den Brande JL, Van Wyk JJ. On the nomenclature of the somatomedins and insulin-like growth factors. J Clin Endocrinol Metab. 1987 Nov; 65(5):1075-1076. PubMed 3667879

DeGroot LJ, Jameson JL, eds. Endocrinology. 4th ed. Philadelphia, Pa: WB Saunders Co; 2001:2257-2268.

Pearson OH, Arafah B, Brodkey J. Management of acromegaly. Ann Intern Med. 1981 Aug; 95(2):225-227. PubMed 7258874

Pintor C, Loche S, Cella SG, Müller EE, Baumann G. A child with phenotypic Laron dwarfism and normal somatomedin levels. N Engl J Med. 1989 Feb 9; 320(6):376-379. PubMed 2913494

Rappaport R, Prevot C, Brauner R. Somatomedin-C and growth in children with precocious puberty: a study of the effect of the level of growth hormone secretion. J Clin Endocrinol Metab. 1987 Dec; 65(6):1112-1117. PubMed 3680478

Underwood LE, D'Ercole AJ. Anterior pituitary gland and hypothalamus: Disorders affecting anterior pituitary function. In: Rudolph AM, Hoffman JI, eds. Pediatrics. 18th ed. Norwalk, Conn: Appleton & Lange;1987:1454-1465.

Watts NB, Keffer JH. Anterior pituitary and hypothalamus. Practical Endocrinology. 4th ed. Philadelphia, Pa: Lea & Febiger;1989:11-36.

Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.