Leptin (human), recombinant, is primarily used in research and clinical settings to study metabolic regulation and energy balance. It plays a key role in modulating appetite and body weight by signaling satiety to the hypothalamus, making it valuable in obesity and metabolic disorder studies. Recombinant leptin is used to treat conditions associated with leptin deficiency, such as congenital leptin deficiency and lipodystrophy, where it helps reduce hunger, lower food intake, and improve glucose metabolism. It is also investigated for its potential in managing insulin resistance, type 2 diabetes, and hypothalamic amenorrhea. In research, it serves as a tool to explore the mechanisms of energy homeostasis, neuroendocrine function, and immune modulation, given leptin's role in linking metabolism with immune response.