Desensitization
The progressive reduction in a cell's or receptor's response to a compound following repeated or prolonged exposure, resulting in diminished effect over time.
Desensitization occurs when receptors are internalized, downregulated, or uncoupled from their signaling pathways after sustained stimulation. In peptide research, this is a practical concern with compounds like GHRPs — continuous infusion or excessive dosing frequencies can blunt the growth hormone pulse response as pituitary receptors desensitize.
This is one reason pulsatile dosing protocols (discrete injections that mimic natural rhythms) are preferred over continuous administration for many research peptides. Cycling compounds — alternating periods of use with periods of rest — is also commonly used to allow receptor sensitivity to recover and restore full responsiveness.