Effect van tekort en suppletie van groeihormoon en insuline-achtige groeifactor-I op hersenfuncties

Abstract

Growth hormone (GH) and insulin-like growth factor 1 (IgF-1) are important for brain functioning. There are GH and IgF-1 receptors in numerous brain areas and cognitive impairments in patients with GH deficiency (GHD), Prader Willi syndrome (PWS), traumatic brain injury (TBI) and dementia seem related to low levels of these hormones. Also agerelated cognitive decline appears to be associated with reduced GH/IgF-1 levels. As GH substitution can alter hormone levels in the cerebral spinal fluid it may affect brain functioning. Indeed, a minimum duration of one year of GH substitution improved cognitive functioning of GHD patients. In Alzheimer patients the administration of a GH secretagogue substantially enhanced IgF-1 levels, but did not induce positive psychological effects. In contrast, one study on GH substitution in PWS patients indicated positive cognitive effects. As transient or permanent GHD frequently occurs in TBI patients, GH substitution may reduce brain impairment. The only study that investigated GH substitution in TBI patients indeed reported a beneficial effect of GH substitution on cognition, including memory. We conclude that GH substitution may reduce cognitive impairment or even improve brain functions in specific patient groups. Although GH substitution has been shown to improve cognitive functioning in various groups, effects are sometimes small and study groups are frequently heterogeneous with a small sample size. As the available evidence of the cognitive effects of GH substitution is limited, more studies are needed to demonstrate that GH substitution may induce cognitive improvement in distinctive patient groups with GHD.