PRL and obesity due to melanocortin 4 receptor deficiency: Noteworthy, clinical studies in humans seem to indicate a U-shaped relationship between PRL levels and cardiometabolic risk, as both hyper- and hypoprolactinemia have been associated with various metabolic complications, including obesity, impaired glyco-insulinemic and lipid profiles, and metabolic syndrome (MetS) [38, 51, 62, 63].