Retatrutide is a triple receptor agonist, engineered to act simultaneously on GIP, GLP-1, and glucagon receptors, extending the dual-agonist approach seen in compounds like tirzepatide with an additional glucagon receptor pathway. Glucagon receptor activity is of particular research interest because, unlike the incretin pathways alone, it is associated with increased energy expenditure and hepatic lipid metabolism, alongside the appetite-suppressing and glucose-regulating effects shared with GIP and GLP-1 signalling. This combined three-pathway mechanism has made retatrutide a focus of research into body composition, lipid handling, and metabolic rate, with particular attention paid to how the added glucagon component may differentiate its effects from dual-agonist and single-pathway compounds studied previously.