Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive, and psychiatric impairments, partly due to disruptions in neurotrophin signaling. Brain-derived Show more
Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive, and psychiatric impairments, partly due to disruptions in neurotrophin signaling. Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3) play critical roles in neuronal survival, synaptic plasticity, and neuroprotection, yet their alterations across biofluids and brain regions in HD remain unclear. This study systematically reviewed and meta-analyzed human and rodent studies to quantify neurotrophin changes and explore moderating factors. Comprehensive searches of PubMed, Scopus, Web of Science, Embase, Google Scholar, and clinical trial registries were conducted up to December 2025. Studies reporting measurable BDNF, NGF, or NT-3 levels in HD patients or animal models were included. Data were extracted on neurotrophin type, sample source, subject characteristics, and measurement methods. Standardized mean differences were calculated using random-effects models, and meta-regression was applied to evaluate the effects of species, sex, sampling region, and analytical techniques. The results showed a significant decrease in neurotrophin levels in both peripheral biofluids and central brain regions in HD. The results for moderator analyses showed that species and sex significantly affected the magnitude of changes in ELISA-based studies, whereas molecular methods consistently detected reductions irrespective of these factors. No significant publication bias was identified. These findings highlight significant neurotrophic deficits in HD, highlight the importance of biological and methodological considerations in interpreting neurotrophin data, and suggest that peripheral neurotrophin measurements may serve as accessible biomarkers for disease progression. Show less