Key amongst these are 5‐HT circuits and, correspondingly, various therapeutics target components of this system, particularly the 5‐HT2CRs. Weight loss commonly improves type 2 diabetes and, as such, 5‐HT obesity drugs would be expected to improve glycaemic control and insulin sensitivity in patients with type 2 diabetes. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.