Effect of growth hormone replacement on cerebral glucose metabolism and blood flow in adults with growth hormone deficiency: A preliminary report

Four patients with growth hormone deficiency (GHD) have been studied using positron emission tomography (PET) to examine the effects of growth hormone (GH) replacement on cerebral metabolic rate for glucose and cerebral blood flow. The parameters were measured regionally in brain volumes previously defined on high-definition, contiguous, magnetic resonance images co-registered to the PET data. The initial rate of cerebral glucose consumption was found to be lower in patients with GHD (0.26 mu mol/g/minute; n = 4) than in normal volunteers (0.36 mu mol/g/minute; n = 6). Following GH replacement therapy, the initial rate of cerebral glucose consumption in patients with GHD was consistently and globally raised (0.32 mu mol/g/minute; P = 0.05; n = 4). The results from cerebral blood flow studies show no changes following GH replacement. These preliminary data suggest that GHD results in a reduced cerebral metabolic rate (which may explain some of the psychological effects of the condition) and that GH replacement therapy has an effect upon the central nervous system.