Standard and low-dose IGF-I generation tests and spontaneous growth hormone secretion in children with idiopathic short stature

Summary objective Abnormalities in the GH–IGF‐I axis, consistent with GH insensitivity (GHI), have been reported in some patients with idiopathic short stature (ISS). The standard IGF‐I generation test (IGFGT) has not demonstrated mild GHI in subjects with ISS. The aim of this study was to investigate the GH–IGF‐I axis in ISS by performing standard and novel low‐dose IGFGTs together with determination of spontaneous GH secretion. patients and methods Twenty‐one (17 male) prepubertal children with ISS, mean age 8·3 years (4·5–12·2), mean height −3·48 SD (−5·40 to −1·79), mean peak GH to provocation with glucagon/clonidine 32·3 mU/l (14·1–66·0) were studied. Serum IGF‐I and IGFBP‐3 levels were measured during standard (GH 0·033 mg/kg/day × 4) and low (GH 0·011 mg/kg/day × 4) dose IGFGTs at 0, 12, 36 and 84 h. The low‐dose IGFGT was performed in seven naive GH‐deficient patients (4 male), mean age 8·5 years (range 4·1–11·1). Determination of spontaneous 24‐h GH secretion was performed in the 21 ISS patients. results Basal IGF‐I and IGFBP‐3 standard deviation scores (SDS) in ISS patients were −1·39 (−2·4–1·16) and −0·45 (−1·13–0·38), respectively, IGF‐I being lower than IGFBP‐3 (P