What hormone acts counter-regulatory to insulin and is stimulated by hypoglycemia?

The hormone that acts counter-regulatory to insulin and is stimulated by hypoglycemia is glucagon. When blood glucose levels drop, glucagon is secreted by the alpha cells of the pancreas. Its primary role is to raise blood glucose levels by promoting gluconeogenesis and glycogenolysis in the liver, which helps to restore glucose levels to a normal range.

In addition, glucagon plays a critical role in the body's overall glucose homeostasis, particularly during periods of fasting or low carbohydrate intake. This action is essential for maintaining energy balance, especially in situations when the body's immediate energy source, glucose, becomes limited.

While other hormones such as cortisol and adrenaline also have counter-regulatory effects on insulin and can be involved in increasing blood glucose under stress or low blood sugar conditions, glucagon is the primary hormone directly stimulated by hypoglycemia to counteract falling glucose levels.