CCK and obesity due to melanocortin 4 receptor deficiency: Consequently, CCK biology has now opened windows for insights into pathophysiology with diagnostic and therapeutic possibilities in metabolic disorders (obesity, eating disorders, and diabetes mellitus), gallbladder disease, neuropsychiatric diseases (cerebral tumors, memory, and anxiety disorders), cardiac diseases (prognosis in heart failure), neuroendocrine and pediatric tumors, as well as perhaps infertility.