Which hormone primarily regulates blood sugar levels?

Insulin is the primary hormone responsible for regulating blood sugar levels. It is produced by the beta cells of the pancreas and plays a crucial role in facilitating the uptake of glucose by cells, particularly in muscle and fat tissues. When blood sugar levels rise after eating, insulin is released into the bloodstream, promoting the storage of glucose as glycogen in the liver and allowing cells to utilize glucose for energy. This regulation helps maintain homeostasis in blood sugar levels, preventing them from becoming too high (hyperglycemia) or too low (hypoglycemia).

While glucagon, produced by the alpha cells of the pancreas, also plays a role in blood sugar regulation by increasing blood glucose levels when they are low, it functions in a complementary manner to insulin and is not the primary regulator. Adrenaline and cortisol can influence blood sugar levels during stress by promoting glucose release from the liver, but they do so under different physiological circumstances and are not the primary regulators in the normal state. Thus, insulin is the most critical hormone for maintaining normal blood sugar levels in the body.