Abstract
Children with idiopathic short stature (ISS) may have normal or increased growth hormone (GH) responses to provocation tests and achieve a final height (FH) below –2.0 standard deviation score (SDS) if untreated. FH of subjects with high stimulated GH levels has not been studied in detail. Aim: It was the aim of this study to analyse FH in ISS patients with high GH peak responses to the provocation test. Patients andMethods: We studied 16 patients (9 pre-pubertal) with ISS and a GH peak ≧40 mU/l to insulin-induced hypoglycaemia. The patients were recalled at age 19.7 ± 2.5 years for measurement of FH when blood samples were obtained for serum insulin-like growth factor (IGF)-I, IGF binding protein 3, acid-labile subunit and GH binding protein measurements. GH bioactivity was determined using the Nb2 bioassay. Results: FH was –3.1 ± 1.0 SDS, being significantly lower than target height (TH). At FH, IGF-I levels were within –1.5 and +1.5 SDS for age and sex in 10 patients and higher than +1.5 SDS in 6 patients. IGF binding protein 3, acid-labile subunit, GH binding protein levels and GH bioactivity values were normal. Summary: These data suggest that patients with ISS and high GH levels during a GH stimulation test may have a more compromised FH. The association of severe ISS with a peak GH >40 mU/l might suggest a degree of insensitivity for the GH-IGF-I axis.
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