Growth Hormone Treatment Improves Cognitive Function in Short Children with Growth Hormone Deficiency

Background/Aims: We investigated the association between cognition and growth hormone (GH) status and GH treatment in short prepubertal children with broadly ranging GH secretion. Methods: A total of 99 children (age 3-11 years), 41 with GH deficiency (GHD) and 58 with idiopathic short stature (ISS), were randomized to a fixed dose (43 µg/kg/day) or a prediction model-guided individualized dose (17-100 µg/kg/day) and followed up for 24 months. In a longitudinal and mixed within- and between-subjects study, we examined clinical effect size changes, measured by Cohen's d, in full-scale IQ (FSIQ) and secondary IQ indices. Results: Significant increases giving medium effect size in FSIQ (p = 0.001, Cohen's d = 0.63), performance IQ (p = 0.001, Cohen's d = 0.65) and processing speed (p = 0.005, Cohen's d = 0.71) were found in the GH-deficient group. In contrast, perceptual organization only increased in the ISS group (p = 0.001, Cohen's d = 0.53). Baseline IQ was normally distributed with small but significant differences between the groups: GH-deficient children had lower FSIQ (p = 0.042) and lower performance IQ (p = 0.021). Using multiple regression analysis, 40% of the variance in delta processing speed scores (0-24 months) was explained by GHmax and IGF-ISDS at baseline. Conclusion: IQ, specifically fluid intelligence, increased in the GH-deficient children. The pretreatment status of the GH/IGF-I axis was significantly predictive for these changes.