The effects of growth hormone (GH) deficiency and GH replacement on cognitive performance in adults: A meta-analysis of the current literature

Objective: There is growing evidence in the neuropsychological literature that growth hormone (GH) deficiency is associated with cognitive impairment. There is also evidence that this impairment may be ameliorated with GH replacement therapy. The current study assessed the nature and severity of cognitive impairment associated with growth hormone deficiency, as well as effect of GH replacement on cognitive function by conducting a-meta-analysis of the published literature to date. Method: Thirteen studies met the inclusion criteria and these included: five cross-sectional studies investigating GH deficiency; and, eight (eight prospective, two of which also included cross-sectional comparisons) investigating GH replacement. Effect sizes (Cohen's d) fatting into six cognitive domains were computed (separately for GH deficiency and GH replacement). Results: For GH deficiency, each of the cognitive domains assessed (besides language) showed moderate to Large impairments when compared to matched controls (Effect sizes -0.46 to - 1.46). For GH replacement, even though treated patients still performed moderately to largely below that of controls, when compared to their own baselines (as in prospective analyses), moderate improvements were found in cognitive performance, particularly attention and memory. Conclusion: This meta-analysis clearly demonstrates the link between GH and cognitive performance, where poor performance can be ameliorated with GH treatment. (c) 2006 Elsevier Ltd. All rights reserved.