desensitization
Desensitization is the cell growing deaf to a message it keeps hearing. If a hormone signal persists, the cell gradually responds less and less, the way you stop noticing a smell that lingers in a room — the signal is still there, but it no longer commands attention.
It works through several mechanisms acting over different timescales. The fastest is chemical modification of the receptor itself: signaling proteins phosphorylate the active receptor and recruit proteins that uncouple it from its G protein, quieting it within seconds to minutes. Over longer periods, the cell internalizes receptors and reduces their number — receptor downregulation — deepening and prolonging the reduced response.
Desensitization protects cells from being overwhelmed by constant signaling and lets responses adapt to background hormone levels. Clinically it explains tachyphylaxis — the rapid loss of a drug's effect with repeated or continuous use — and is why some hormone-based treatments work better when given in pulses that allow receptors to recover.
Continuous use of a GnRH analog first stimulates, then desensitizes pituitary cells, ultimately suppressing LH and FSH — a strategy used to treat prostate cancer and endometriosis.
Desensitization turned into a deliberate therapeutic tool.
Desensitization and downregulation overlap but are not identical: desensitization is the broad loss of response, while downregulation refers specifically to having fewer receptors as one of its mechanisms.