Leptin is a protein that is secreted by white adipocytes, and which plays a major role in the regulation of body weight. Leptin is the most critical hormone in the homeostatic regulation of energy balance among those so far discovered. Leptin primarily acts on the neurons of the mediobasal part of hypothalamus to regulate food intake, thermogenesis, and the blood glucose level. Leptin also has several endocrine functions, and is involved in the regulation of immune and inflammatory responses, hematopoiesis, angiogenesis and wound healing. Mutations in this gene and/or its regulatory regions cause severe obesity, and morbid obesity with hypogonadism. Leptin has also been linked to type 2 diabetes mellitus development.