MC4R and obesity due to melanocortin 4 receptor deficiency: Other mutations within the leptin–melanocortin pathway, such as in proopiomelanocortin (POMC), melanocortin receptor 4 (MC4R), brain-derived neurotrophic factor (BDNF), and the tyrosine kinase receptor B (NTRK2) genes, can also contribute to obesity [70,71].