We quantified expression of chromogranin A, glucagon‐like peptide‐1 (GLP‐1), serotonin, and neuromedin U (NmU) in duodenal biopsies from 34 participants with obesity (19 with T2D, 15 without) and six healthy controls. The gene discussed is NMU; the disease is obesity due to melanocortin 4 receptor deficiency.