HMM: Study reveals biology of leptin, the hunger hormone. “The researchers discovered that the mechanisms by which reductions in plasma leptin concentrations stimulate food intake are not limited to the brain, as previously thought. In rodents, fasting first activates leptin receptors in the brain, followed by an intermediary step that involves the endocrine system. This system includes the pituitary and adrenal glands, which secrete another hormone, corticosterone, that regulates energy, stress responses, and food intake. The research team learned that this chain of events is required for leptin to stimulate hunger when food is restricted, or when diabetes is poorly controlled and plasma leptin concentrations drop below a critical threshold.”