NPPB and obesity due to melanocortin 4 receptor deficiency: Potential resilience to common confounders: Given that NT-proBNP is depressed in obesity and altered by CKD/AF, a structurally anchored marker like Cav-3 could retain signal where peptides are noisier—an inference that warrants direct testing in enriched obese/CKD/AF subgroups (13, 14).