Which hormone raises blood glucose and signals the liver to release stored glucose?

The hormone that raises blood glucose levels and signals the liver to release stored glucose is glucagon. Glucagon is produced by the alpha cells of the pancreas and plays a critical role in glucose metabolism. When blood sugar levels drop, glucagon is released into the bloodstream, prompting the liver to convert stored glycogen into glucose and release it into the circulation. This process helps to increase blood glucose levels and ensure that the body has enough energy to function properly, particularly during periods of fasting or between meals.

In contrast, insulin lowers blood glucose levels by facilitating the uptake of glucose into cells and promoting the storage of glucose as glycogen in the liver. Somatostatin regulates the endocrine system and inhibits the release of several hormones, including insulin and glucagon, but does not directly raise blood glucose levels. Progesterone is a hormone associated with the menstrual cycle and pregnancy, with no direct role in glucose metabolism or blood glucose regulation.