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 insulin-like 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 stature 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 ternary complex (IGF-I, IGF-binding protein-3 (IGFBP-3), acid-labile subunit (ALS), and IGF-I/IGFBP-3 ratio) were evaluated as biomarkers for the respective diagnosis. Results All the components of the ternary complex were tightly correlated with each other and were positively related to age. IGF-I, IGFBP-3, ALS, and IGF-I/IGFBP-3 ratio differed significantly 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 groups 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 diagnosis.