Question

Insulin secretion is inhibited by:

• A. Secretin
• B. Epinephrine
• C. Growth hormone
• D. Gastrin

Hint:

Stress hormones acting on alpha-2 receptors switch insulin off.

Answer 1

The Correct Option is B

Step 1: Insulin is released from the beta cells of the pancreatic islets. Its secretion is controlled by nutrients, hormones, and the autonomic nervous system.
Step 2: Epinephrine inhibits insulin secretion. It acts on alpha-2 adrenergic receptors on the beta cell, which lower cyclic AMP and suppress insulin release. This makes sense during stress and the fight or flight response, when the body needs to keep blood glucose high for energy rather than store it.
Step 3: The other options actually promote insulin secretion. Secretin and gastrin are gut hormones with an incretin-like effect that augments insulin release after a meal. Growth hormone, although it antagonises insulin action over time and is diabetogenic, stimulates insulin secretion and over the long term tends to raise insulin levels.
Step 4: So the only option that directly inhibits insulin secretion is epinephrine, acting through alpha-2 receptors.
Conclusion: Insulin secretion is inhibited by epinephrine. Answer is option B.