Growth Hormone and Brain Regeneration: Evidence from Clinical Studies in Dementia, Traumatic Brain Injury, and Stroke: A Systematic Review.

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) play essential roles in the brain, influencing neuronal and dendritic growth, as well as neurotransmission. These effects persist throughout life. Numerous studies in animals and humans have demonstrated the beneficial effects of GH therapy on memory and cognitive function, as well as on the restoration of neuronal function following injury. All nerve cells, including neurons, glia, endothelial, epithelial, and perivascular cells, are affected by the actions of GH/IGF-1. IGF-1, in particular, has been associated with cognitive function. The GH-IGF-1 axis increases the proliferation of neuronal progenitor cells and the formation of new neurons, oligodendrocytes, and astrocytes. In this study, we searched databases such as PubMed, Google Scholar, and Embase for human clinical trials evaluating the effect of growth hormone (GH) therapy on dementia, Alzheimer's disease (AD), post-traumatic brain injury (PTI), and stroke. The following search terms were used: "GH and dementia," "GH and Alzheimer's disease," "GH and TBI," and "GH and stroke." Inclusion criteria were all randomized controlled trials and observational studies. Exclusion criteria included the lack of cognitive and memory assessments. We found 28 articles. Most studies show the beneficial effects of GH therapy on memory and recovery of brain function after traumatic injury and stroke; however, consistent data are still lacking. The limited number of clinical trials, the small number of patients, and the lack of data on plasma levels of sex hormones that clearly contribute to brain function are limiting factors. This is the case, for example, with androgens. Other critical factors are dosage and treatment duration. Prolonged administration and supraphysiological doses are more effective in inducing positive clinical changes. Growth hormone (GH) therapy is a very promising intervention for preventing and treating dementia and early-stage Alzheimer's disease, and it contributes significantly to the recovery of brain function in patients after traumatic injury and stroke. Further studies with more robust methodologies are needed to confirm these results.