A counterregulatory hormone is a hormone that opposes the action of insulin. They include glucagon, adrenaline, cortisol, and growth hormone. Counterregulatory hormones — the term is usually used in the plural — raise the level of glucose in the blood by promoting glycogenolysis, gluconeogenesis, ketosis, and other catabolic processes. In healthy people, counterregulatory hormones constitute a principal defense against hypoglycemia, and levels are expected to rise as the glucose falls. Persistent elevation of a counterregulatory hormone can reduce a person’s sensitivity to insulin.