Several mechanisms can result in NMDRs, including biological feedback loops, receptor saturation, and changes in gene expression. For example, low doses of a chemical might activate a protective response in the body, while higher doses overwhelm this mechanism, resulting in a different response. In endocrine systems, low doses of a hormone mimic might exert an effect by binding to hormone receptors, but higher doses could result in receptor desensitization or downregulation, altering the response.
