Final answer:
Glucagon, released from the alpha-cells of the pancreas, promotes gluconeogenesis in the liver, especially during low blood glucose levels like fasting or exercise.
Step-by-step explanation:
The hormone that is released from the pancreas and generally promotes gluconeogenesis in the liver is called glucagon. This hormone is a peptide consisting of 29 amino acids with a molecular weight of 3485 Da. Glucagon is secreted by the alpha-cells of the islets of Langerhans in the pancreas when blood glucose levels start to fall, such as during fasting, starvation, or severe exercise. By activating hepatic adenyl cyclase, glucagon promotes glycogen breakdown (glycogenolysis), gluconeogenesis from substrates like lactate and amino acids, and it also has effects on lipid metabolism like lipolysis and ketone body formation.
Glucagon's primary role is to increase the level of glucose in the blood, counteracting the hypoglycemic effects of insulin. Insulin and glucagon work together in a negative-feedback system that maintains blood glucose stability. In conditions where insulin is insufficient or ineffective, such as in diabetes mellitus, glucagon's hyperglycemic effects can exacerbate high blood sugar levels.