Your body already makes a hormone that tells your skin to tan. Melanotan 2 is a synthetic peptide engineered to mimic that hormone but in a version that's more potent and longer lasting than Fat loss can be triggered through the brain in animal model, researchers find UF Health Melanotan II (Tan Jabs): Why They're Not Worth The Risk Eruptive naevi and darkening of preexisting naevi 24 h after a single mono dose injection of melanotan II Semantic Scholar