Ghrelin concentration is correlated with IGF-I/IGFBP-3 molar ratio but not with GH secretion in children with short stature

OBJECTIVES: In children with growth hormone deficiency (GHD) and neurosecretory dysfunction (NSD) ghrelin concentrations are significantly higher than in children with idiopathic short stature (ISS), however the correlation between serum ghrelin and growth hormone (GH) is not observed. The aim of the study was to compare ghrelin concentrations with IGF-I/IGFBP3 molar ratio in children with short stature due to different etiology. MATERIAL: Analysis comprised 136 children (58 girls and 78 boys), aged 3.86-16.82 years with short stature (below -2.0 SD); in 21 of them GHD was diagnosed, in 23 - NSD and 92 - ISS. In each child, fasting ghrelin, insulin-like growth factor type I (IGF-I) and its binding protein type 3 (IGFBP-3) concentrations were measured. The results were analysed separately in younger and in older children. Depending on IGF-I/IGFBP-3 molar ratio, children were divided into two (2) groups: with lower IGF-I/IGFBP-3 and with higher IGF-I/IGFBP-3 ratio value. RESULTS: Both in younger and in the older age groups, ghrelin concentration was significantly higher in children with lower IGF-I/IGFBP-3 ratio than in children with higher IGF-I/IGFBP-3 value (1937.3 +/- 1232.4 vs 1365.3 +/- 632.1 pg/ml in younger children and 1205.4 +/- 548.8 vs 867.4 +/- 282.9 pg/ml in older children). The negative correlation between ghrelin and IGF-I/IGFBP-3 ratio was observed in both age groups. Not only children with GHD and NSD, but also as much as 39% out of all children with ISS were qualified into the subgroups with lower IGF-I/IGFBP-3 ratio. CONCLUSIONS: Ghrelin secretion is elevated in children with lower IGF-I/IGFBP-3 ratio. It seems that lower bioactivity of IGF-I is stimulating factor for ghrelin synthesis.