PCSK1 and autoimmune polyendocrinopathy: The intestinal enteroendocrine cells have a key role in the regulation of food intake, glucose homeostasis, digestion, and absorption.20,21 Defects of the enteroendocrine system are causative for the congenital intestinal diarrheal diseases in a small number of Mendelian diseases, congenital malabsorptive diarrhea (MIM 610370), prohormone convertase 1/3 deficiency (MIM 600955), and autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy syndrome (MIM 240300).