Growth hormone treatment adjusted for growth hormone sensitivity in idiopathic short stature.

Objective: This study aimed to investigate the long-term growth responses to recombinant human growth hormone (rhGH) in children with idiopathic short stature (ISS), decreased IGF-1 levels and a normal stimulated GH peak, after assessing their GH sensitivity using the IGF-1 generation test (IGFGT).

Design: Retrospective descriptive case series.

Methods: 129 children with height <-2.5 SDS, IGF-1 <-2.0 SDS on two occasions, and peak GH >10 µg/L, underwent an IGFGT to be categorized into normal (neurosecretory dysfunction), intermediate, or low GH sensitivity. The first group was treated with a rhGH substitution dose (0.025-0.035 mg/kg) and the others with a higher dose (0.035-0.050 mg/kg). Patients were followed for at least one year, with 58 patients reaching near-adult height (NAH). Prepubertal and pubertal patients were analysed separately.

Results: During the first year of treatment in prepubertal patients, height increased by 0.8±0.4 SDS, height velocity by 4.0±2.1 cm/year, and predicted adult height (PAH) by 0.6±0.7 SDS. At NAH, average height was -1.0±1.0 SDS, which is 2.1±0.8 SDS higher than height at start, 1.5±0.8 SDS higher than PAH at start, and 0.3±0.9 SDS below target height. No group differences were observed. Using the rhGH treatment prediction models from the KIGS database, patients performed better than expected for ISS, and similar to patients with idiopathic isolated GH deficiency.

Conclusion: Children with ISS, decreased IGF-1 levels and a normal stimulated GH peak show a good response to rhGH treatment. The IGFGT is a useful tool for selecting this subgroup from ISS patients and optimizing rhGH dose.