Insulin-like growth factor ternary complex components as biomarkers for the diagnosis of short stature.

Objective: The diagnosis of growth hormone deficiency (GHD) in children is not always straightforward because insulinlike growth factor 1 (IGF-I) or GH stimulation tests may not be able to discriminate GHD from constitutional delay of growth and puberty (CDGP) or other causes of short stature. Design: Boys and girls (n = 429, 0.7-16 years) who attended our department for short statu re participated in this study. They were followed up for an average period of 9 years. At the end of follow-up after reaching the final height, a definitive diagnosis was assigned, and all the components of t ernary complex (IGF-I, IGF-binding protein-3 (IGFBP-3), acid-labile subunit (ALS), and IGF-I/IGFBP-3 ratio) were evalua ted as biomarkers for the respective diagnosis. Results: All the components of the ternary complex were tightly correla ted with each other and were positively related to age. IGF-I, IGFBP-3, ALS, and IGF-I/IGFBP-3 ratio differed si gnificantly between GHD and normal groups. IGF-I and ALS levels were lower in GHD compared to children with familial short stature, while IGF-I and IGF-I/IGFBP-3 ratio was significantly lower in GHD compared to children with CDGP. IGF-I and IGF-I/IGFBP-3 receiver operating curve cutoff points were unable to discriminate between GHD and normal group s or between GHD and CDGP groups. Conclusion: Despite the tight correlation among all the components of the ternary complex, each one shows a statistically significant diagnosis-dependent alteration. There is a superiority of IGF-I, ALS, and IGF-I/IGFBP-3 ratio in the distinction between GHD and CDGP or between GHD and normal groups but without usable discriminating power, making auxology as the primary criterion for establishing the d iagnosis. [ABSTRACT FROM AUTHOR]