GLP1R and obesity due to melanocortin 4 receptor deficiency: Although not usually associated with type 2 diabetes or obesity, the glucagon family of receptors also includes the GLP-2 receptor (GLP-2R), which is activated by GLP-2, a 33-amino acid peptide (GLP-2(1–33)) also derived from pre-proglucagon and secreted mainly from enteroendocrine L cells, like GLP-1.