Which hormone is primarily involved in the body's response to low blood sugar during stress?

The hormone that plays a crucial role in the body's response to low blood sugar during stress is glucagon. When blood sugar levels drop, particularly in stressful situations, glucagon is secreted by the alpha cells of the pancreas. Its primary function is to raise blood glucose levels by promoting the conversion of glycogen (stored glucose) in the liver into glucose, which is then released into the bloodstream. This process is essential for maintaining energy supply during stress or fasting.

While cortisol and adrenaline are also involved in the body's stress response, their roles differ from that of glucagon. Cortisol helps regulate metabolism and can influence blood sugar levels indirectly by promoting gluconeogenesis; however, glucagon is the primary hormone specifically designed to counteract low blood sugar levels. Adrenaline (also known as epinephrine) can facilitate mobilization of energy stores and increase heart rate, but it does not directly stimulate glycogenolysis and gluconeogenesis to the same extent as glucagon.

Thyroid hormone, though critical for metabolism and overall energy regulation, is not directly involved in the immediate response to low blood glucose during stress. Therefore, glucagon is the key hormone responding to low blood sugar under stressful conditions, making it the correct choice.