This hypothesis was tested also by drawing analogies between GPR61 and MC4R. MC4R is a well-characterized receptor involved in regulating appetite and its variants are the key contributors to monogenic obesity, affecting satiety signals and homeostasis energy expenditure (Farooqi et al, 2003; Doulla et al, 2014; Lotta et al, 2019; Aykut et al, 2020; Brouwers et al, 2021; Metzger et al, 2024). Here, MC4R is linked to obesity due to melanocortin 4 receptor deficiency.