Which hormone counters the effects of insulin?

• A. Glucagon
• B. Adrenaline
• C. Cortisol
• D. Thyroxine

Answer: (A)

Glucagon is the hormone that counteracts the effects of insulin. When blood sugar levels drop, glucagon is secreted by the pancreas to stimulate the liver to convert stored glycogen into glucose, releasing it into the bloodstream. This process helps to raise blood glucose levels, effectively opposing the action of insulin, which lowers blood glucose by facilitating the uptake of glucose into cells.

Insulin and glucagon work together to maintain glucose homeostasis in the body, balancing the levels to ensure that energy is available as needed. While adrenaline, cortisol, and thyroxine can influence metabolism and blood sugar levels, their primary roles are different, and they do not specifically counteract insulin in the same direct way that glucagon does. Adrenaline, for example, primarily prepares the body for a "fight or flight" response and can increase blood sugar levels, but it does not function as a direct counter to insulin like glucagon. Similarly, cortisol is a stress hormone that regulates metabolism but is involved in more complex pathways. Thyroxine primarily regulates metabolism and growth but does not directly counteract insulin.