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IGF-1 measurements can be useful when evaluating patients of gestational age1 who are suspected of being (1) growth hormone-deficient2 or (2) acromegalic.3
Plasma specimens may produce falsely elevated or decreased results. The IGF-1 reference intervals by pubertal Tanner stages reflect ranges and means based on asymmetric curves. Z scores are calculated based on the asymmetric curves with transformed data. Patient gender and date of birth must be provided in order to calculate a z score. Z scores will not be calculated for patients younger than three years or older than 18 years.
Insulin-like growth factor 1 (IGF-1) is a polypeptide hormone that can affect growth-promoting activity and glucose metabolism. IGF-1 exists in a three-subunit complex form, with IGF-1 or IGF-2 (υ-subunit), IGFBP-3 (β-subunit), and acid labile subunit (ALS) (α-subunit). Samples are acid:ethanol extracted to remove IGF-1 from the complex, resulting in a consistent IGF-1 measurement, even with variable binding protein levels. The extracted sample is then analyzed by radioimmunoassay using a highly specific antibody.4
1. Lee PA, Chernausek SD, Hokken-Koelega ACS, et al. International Small for Gestational Age Advisory Board Consensus Development Conference Statement: Management of short children born small for gestational age. April 24-Oct 1, 2011. Pediatrics. 2003; 111(6):1253-1261. PubMed 12777538
2. GH Research Society. Consensus guidelines for the diagnosis and treatment of the GH Research Society. J Clin Endocrinol Metab. 2000; 85(11):3990-3993. PubMed 11095419
3. Giustina A, Chanson P, Bronstein MD, et al. A consensus on criteria for cure of acromegaly. J Clin Endocrinol Metab. 2010; 95(7):3141-3148. PubMed 20410227
4. Alberti C, Chevenne D, Mercat I, et al. Serum concentrations of insulin-like growth factor (IGF-1) and IGF binding protein-3 (IGFBP-3), IGF-1/IGFBP-3 ratio, and markers of bone turnover: Reference values for French children and adolescents and Z-score comparability with other references. Clin Chem. 2011; 57(10):1424-1435. PubMed 21865482
