Insulin-like Growth Factor-1 (IGF-1) With Z Score

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-1.¹³ Reference intervals for IGF-I using the IDS IGF-I were determined in a clinical routine study population from the United States.^13,14 The cohort included 778,173 males and 710,752 females, aged from 0 to 90 years, who were representative of the overall United States population in terms of gender, race and ethnicity. Reference intervals were adjusted for age and sex using a modified Hoffman approach.¹⁵