Which hormone's primary function is to lower blood glucose levels?

The hormone that primarily functions to lower blood glucose levels is insulin. Produced by the pancreas, specifically by the beta cells within the islets of Langerhans, insulin facilitates the uptake of glucose into cells, particularly muscle and adipose (fat) tissues. This process not only helps to lower the concentration of glucose in the bloodstream but also promotes the conversion of glucose to glycogen for storage in the liver.

Insulin plays a critical role in maintaining homeostasis of blood sugar levels, especially after meals when glucose intake is elevated. By promoting the use of glucose for energy and storing excess glucose, insulin is essential for regulating blood sugar and preventing hyperglycemia, which can lead to various health complications over time. Additionally, insulin promotes protein synthesis and plays a role in lipid metabolism, further illustrating its importance in overall metabolic processes.

In contrast, other hormones listed, such as glucagon, thyroxine, and cortisol, play different roles in glucose metabolism and are not primarily focused on lowering blood glucose levels.