2024), increase the risk of Alzheimer's disease due to the resulting neurodegeneration (Reyes 2025), and may be associated with brain cortical thickness (Motaghi et al. 2024). In metabolic diseases including DM, the irregular secretion of insulin, leptin, orexins, neuropeptide Y, ghrelin, and cholecystokinin may lead to dysfunctions in the sensation of smell (Gouveri et al. 2014). The gene discussed is HCRT; the disease is metabolic disease.