Which hormone is responsible for raising blood sugar levels?

Glucagon is the hormone responsible for raising blood sugar levels. It is produced by the alpha cells of the pancreas and plays a critical role in glucose homeostasis. When blood sugar levels drop, glucagon is released into the bloodstream. Its primary function is to stimulate the liver to convert glycogen, the stored form of glucose, back into glucose through a process called glycogenolysis. Additionally, glucagon promotes gluconeogenesis, which is the synthesis of glucose from non-carbohydrate sources in the liver. This mechanism effectively increases the levels of glucose available in the bloodstream, counteracting hypoglycemia and providing energy to the body when needed.

The other hormones listed have different functions. Insulin, for instance, is crucial for lowering blood sugar levels by facilitating the uptake of glucose into cells. Secretin and gastrin are involved in digestive processes—secretin regulates water homeostasis and pancreatic function in response to acidity in the small intestine, while gastrin stimulates the secretion of gastric acid to aid digestion in the stomach. Thus, glucagon’s specific action of increasing blood sugar makes it the correct choice for this question.