Adipose tissue also secretes the hormone leptin. Huntington's disease has also been linked to imbalances in leptin and ghrelin levels. This pathway likely transduces signals from leptin, adiponectin, and other signaling molecules. ZD might reduce the secretion of insulin and therefore reduce secretion of leptin. Uncoupling proteins are increased by thyroid hormone, norepinephrine, epinephrine, and leptin. Adiponectin in combination with leptin has been shown to completely reverse insulin resistance in mice. This is similar to the action of leptin; adiponectin and leptin can act synergistically. Grehlin stimulates hunger and the intake of food and leptin acts to signal satiety (fullness). Additionally, adipocytes are responsible for the production of the hormone leptin. LEP-R functions as a receptor for the fat cell-specific hormone leptin. This may be primarily via reduced levels of leptin (the satisfaction hormone). FNIII domains are essential for receptor activation upon leptin binding. Enterocytes also have an endocrine role, secreting hormones such as leptin. To achieve energy homeostasis appetite is regulated by two hormones, grehlin and leptin. They are produced by the digestive tract and by adipose tissue (leptin).