Endocrine Abstracts

Introduction: There is a large body of evidence to suggest that the GH axis plays an important role in brain myelination. However, results from studies in humans with an abnormal GH axis have varied and therefore there remains no consensus as to whether the GH/IGF1 axis plays a significant role in neural development. No previous studies have used diffusion tensor imaging (DTI) a sensitive magnetic resonance imaging (MRI) technique for studying brain white matter tracts, to address this question.

Methods: Fifteen children (mean 8.5 years) with isolated GH deficiency (IGHD) (peak GH to provocation <6.7 μg/l (mean 4.5 μg/l) plus a pathologically low IGF1 concentration for age (mean −2 S.D. for age and sex)), and twelve children (mean 8.3 years) with isolated short stature (ISS) (peak GH to provocation >10 μg/l (mean 14 μg/l), normal IGF1 measurements and growth rate) were studied. All underwent MRI imaging of the brain (DTI sequences acquired) and a comprehensive neuropsychological assessment including the Weschler Intelligence Scale for Children (WISC-IV) and the Movement-ABC (M-ABC) test. The fractional anisotropy (FA) images were processed using tract-based spatial statistics, and automated, observer-independent, voxel-by-voxel whole-brain between-group analysis performed.

Results: Children with IGHD had significantly lower FA (reduced white matter integrity) in the parahippocampal region and temporal lobes bilaterally and performed significantly worse on the perceptual reasoning component of the WISC-IV (P<0.05) and the M-ABC (P<0.009), compared to the ISS control group.

Conclusions: These preliminary findings show that white matter abnormalities are present in specific brain regions in children with IGHD, who are impaired compared to controls in perceptual reasoning and motor performance.

Currently the main aim of GH treatment in children is to optimise final height and maintain bone mass; if GH also has a significant impact on neural development and cognition, then this may have important implications for clinical practice.