What is the primary role of glucagon in glucose homeostasis?

The primary role of glucagon in glucose homeostasis is to increase glucose production in the liver. When blood glucose levels are low, glucagon is released from the pancreas and acts primarily on the liver to stimulate gluconeogenesis and glycogenolysis. Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources, while glycogenolysis is the breakdown of glycogen into glucose. This action raises blood glucose levels, ensuring a steady supply of glucose for energy, particularly during fasting or between meals.

In contrast to this role, stimulating glucose uptake by cells is primarily mediated by insulin, which is released when blood glucose levels are high. Inhibition of insulin secretion occurs as a response to low glucose levels, but this is not the primary function of glucagon. Promoting glycogen storage is also primarily associated with insulin, which facilitates the conversion of excess glucose into glycogen for storage. Therefore, the correct answer reflects glucagon's critical role in elevating blood glucose levels when needed.