Which hormone is primarily responsible for regulating blood glucose levels?

Insulin is primarily responsible for regulating blood glucose levels. It is produced by the beta cells in the pancreas and plays a crucial role in maintaining glucose homeostasis in the body. When blood sugar levels rise, such as after a meal, insulin is released to facilitate the uptake of glucose by cells, allowing them to use it for energy or store it as glycogen in the liver and muscle tissues. This action lowers blood glucose levels, helping to stabilize them within a normal range.

Additionally, insulin works in concert with other hormones, but its primary function is to decrease blood glucose levels, making it the key regulator. The role of glucagon, although significant in raising blood glucose levels when needed, is more about responding to low glucose levels rather than regulating them directly. Adrenaline and cortisol also influence blood sugar by promoting the release of glucose into the bloodstream, typically under stress or low glucose conditions, but they do not primarily govern the lower levels of glucose that insulin manages. Therefore, in terms of direct regulation of blood glucose levels, insulin is the hormone that plays the most critical role.