Final Height in Patients with Idiopathic Short Stature and High Growth Hormone Responses to Stimulation Tests

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.