What hormone is secreted to respond to low blood sugar levels?

Glucagon is the hormone that is secreted in response to low blood sugar levels. When blood glucose levels drop, the pancreas releases glucagon, which plays a critical role in maintaining glucose homeostasis. Glucagon stimulates the liver to convert stored glycogen into glucose through a process called glycogenolysis. This released glucose then enters the bloodstream, raising the blood sugar levels back to a normal range. This mechanism is essential for providing energy to the body's cells, particularly during periods of fasting or intense exercise.

Insulin, on the other hand, is responsible for lowering blood sugar levels after eating by facilitating the uptake of glucose into tissues, which is why it is not released in response to low blood sugar. Prolactin is primarily involved in lactation and does not play a role in glucose regulation. ADH, or antidiuretic hormone, regulates water balance in the body and is not directly involved in blood sugar control. Thus, glucagon is the key hormone that responds to low blood sugar levels to restore balance.