Which hormone counteracts the effects of insulin?

The hormone that counteracts the effects of insulin is glucagon. Insulin and glucagon work together to regulate blood glucose levels, but they have opposing actions. Insulin facilitates the uptake of glucose into cells, lowering blood glucose levels, and promoting the storage of glucose as glycogen in the liver and muscle tissues. When blood glucose levels drop, glucagon is secreted by the alpha cells of the pancreas, signaling the liver to convert stored glycogen back into glucose and release it into the bloodstream. This process helps to increase blood glucose levels when they are too low, effectively counteracting insulin's action.

Cortisol, while it does have effects on glucose metabolism, primarily acts to increase blood glucose levels through gluconeogenesis and not directly in opposition to insulin's functions. Insulin-like growth factor plays a role in growth and metabolism but does not primarily counteract insulin. Adrenaline (epinephrine) can also increase blood glucose levels, especially in acute stress situations, but its main role is not to directly counteract insulin in a routine physiological context. Thus, glucagon is specifically designed to counterbalance insulin's effects in maintaining glucose homeostasis.