LEP and obesity due to melanocortin 4 receptor deficiency: Whilst several hypothalamic-acting, blood-borne hormones – including the active thyroid hormone (T3), oestrogen and glucagon-like peptide-1 (GLP-1) – have been reported to regulate obesity (Larabee et al. 2020), here we will focus on the dysregulation of leptin signalling within the hypothalamus.