GLP-1 stimulates glucose-dependent insulin secretion and inhibits glucagon release, thereby lowering blood glucose but not causing hypoglycaemia.2 GLP-1 receptor agonists also signal at the hypothalamus to regulate satiety and weight.3 This has led to GLP-1 receptor agonists being licensed to promote weight loss in the setting of obesity.4 The gene discussed is GCG; the disease is obesity due to melanocortin 4 receptor deficiency.