I just started a thread in the retatrutide subforum about this, I've been going through exactly what you have been.
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Same as you, the change was more like a light switch than a slow change. After about three months, the effects of reta just almost stopped. Of the three reta receptors:
GLP-1 receptor (glucagon-like peptide-1 receptor) — helps regulate appetite, slow gastric emptying, enhance insulin secretion, and promote satiety.
GIP receptor (glucose-dependent insulinotropic polypeptide receptor, also called gastric inhibitory polypeptide receptor) — supports insulin release and contributes to metabolic regulation.
Glucagon receptor (GCG receptor) — influences energy expenditure, fat metabolism, and other processes like increasing lipolysis.
I'm near certain it's my GLP-1 receptors that have stopped responding. The gastric emptying slowdown has ceased and the appetite regulation and satiety effects have virtually completely gone away.