Prepubertal Children With Obesity Have High Free IGF-1 Levels and Accelerated Growth Despite Reduced Pappalysin Levels

Abstract

Abstract Background Prepubertal children with obesity frequently have enhanced growth, accelerated skeletal maturation, and changes in the growth hormone–insulin-like growth factor (GH–IGF) axis. However, the involvement of pappalysins (PAPP-A, PAPP-A2) and stanniocalcins (STC1, STC2) as regulators of IGF bioavailability has not been studied in obesity. Objective We aimed to determine the effects of childhood obesity and weight reduction on serum levels of PAPP-A, PAPP-A2, STC1, and STC2 and their relationship with IGF bioavailability, growth, and other components of the GH–IGF system. Methods Prepubertal children with severe obesity (150, 50% males/females, age: 7.72 ± 2.05 years, BMI z-score: 4.95 ± 1.70, height z-score: 1.28 ± 1.04) were studied at diagnosis and after a minimum of 0.5 BMI z-score reduction. Two hundred and six healthy age- and sex-matched children were used as controls. Results Children with obesity had decreased serum concentrations of PAPP-A, PAPP-A2 and STC2, but increased total and free IGF-I, intact IGFBP-3, acid-labile subunit (ALS), IGF-II, and insulin levels, with no difference in the free IGF-I/total IGF-I ratio. Neither the standardized body mass index (BMI) nor height correlated with any biochemical parameter analyzed. A decrease in IGF-II, insulin, and ALS with an increase in IGFBP-2 and -5, STC2, and PAPP-A were observed after weight loss. Conclusion Increased circulating total and free IGF-I, insulin, and IGF-II may all contribute to the increased rate of prepubertal growth and bone maturation observed in children with obesity, with STC2 possibly being involved.