What hormone is primarily responsible for regulating blood glucose levels?

The hormone primarily responsible for regulating blood glucose levels is insulin. Insulin is produced by the beta cells of the pancreas and plays a crucial role in lowering blood glucose levels. When you eat, carbohydrates from food are broken down into glucose, which enters the bloodstream. In response to rising blood glucose, the pancreas releases insulin.

Insulin facilitates the uptake of glucose by cells, particularly muscle and fat cells, allowing them to use glucose for energy or store it for future use. This process helps to maintain stable blood glucose levels, preventing hyperglycemia (high blood sugar). Insulin also supports the storage of excess glucose in the liver as glycogen.

In contrast, glucagon, another hormone produced by the pancreas, raises blood glucose levels by promoting the release of stored glucose from the liver. While cortisol and adrenaline are related to stress responses and can influence blood glucose levels indirectly, they are not the primary regulators of glucose on a day-to-day basis as insulin is. Thus, insulin is key for direct glucose regulation, making it the correct answer.