In this foundational entry of the BiohackingU melanocortin series, we explore the five primary melanocortin receptors (MC1R–MC5R) and their unique roles in human physiology. From skin pigmentation and sexual function to appetite regulation and brain signaling, each receptor plays a distinct and powerful part in shaping how our body responds to internal and external stimuli. Whether you’re interested in tanning, metabolism, neurology, or cutting-edge peptide therapies, this guide offers a concise yet thorough breakdown of the melanocortin landscape.