Receptor Desensitization

Chronic receptor agonism can trigger adaptive downregulation — reduced receptor density, reduced binding affinity, or uncoupling from downstream signaling. The researcher experiences this as diminishing returns over time at a fixed dose. Desensitization is compound-specific and pathway-specific; some receptors resist it (GLP-1R is surprisingly robust) while others desensitize quickly (some GH-secretagogue receptors within weeks).

Cycling is the primary countermeasure — off-cycle periods allow receptor resensitization. Dose rotation across mechanistically distinct compounds in the same pathway is another countermeasure. Understanding whether a given protocol faces meaningful desensitization risk determines whether cycling is useful or just cargo-cult.