Which of the following hormones primarily stimulates the glycogenolysis process?

BTSC 3 August 2025

Applied Physiology

Easy

Appeared in: BTSC 3 August 2025

Explanation

Glucagon is the primary hormone that stimulates glycogenolysis, the process of breaking down stored glycogen into glucose.
It is secreted by the alpha cells of the pancreas, specifically in response to hypoglycemia (low blood glucose).
Its main target organ is the liver, where it triggers the conversion of glycogen to glucose, which is then released into the bloodstream to raise blood sugar levels.
This action is diametrically opposed to the function of insulin.

Option A: Aldosterone is a mineralocorticoid hormone that primarily regulates sodium and potassium balance, and consequently, blood pressure. It does not have a direct role in glucose metabolism.
Option B: Insulin has the opposite effect of glucagon. It inhibits glycogenolysis and promotes glycogenesis (the storage of glucose as glycogen) to lower blood sugar levels.
Option C: Calcitonin is involved in calcium homeostasis. It is secreted by the thyroid gland and works to lower blood calcium levels, primarily by inhibiting bone resorption.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of blood glucose and glycogenolysis as background academic context rather than a clinical decision trigger.
Understanding the function of glucagon is crucial for managing hypoglycemic emergencies, particularly in patients with diabetes. Nurses are often responsible for administering glucagon injections when a patient is unconscious or unable to take oral glucose.
A 'Glucagon Emergency Kit' is a standard prescription for many individuals with Type 1 diabetes, and patient/family education on its use is a key nursing responsibility.
What if? If a patient has severe liver disease (e.g., cirrhosis), their liver glycogen stores may be severely depleted. In this scenario, administering glucagon for hypoglycemia would be ineffective because there is no glycogen for it to act upon. The priority intervention would be to administer intravenous dextrose.

How to Approach the Question

First, identify the key physiological process in the question stem: 'glycogenolysis'. Recall or deduce its meaning: 'glyco-' refers to glycogen and '-lysis' means to break down. So, the process is the breakdown of glycogen.
Next, consider the purpose of breaking down glycogen. Glycogen is stored glucose, so breaking it down releases glucose into the blood, raising blood sugar levels.
Evaluate each hormone option based on its primary function in metabolism.
Eliminate Aldosterone (regulates salt/water) and Calcitonin (regulates calcium) as they are not primarily involved in glucose control.
Compare the two remaining options, Insulin and Glucagon, which are the main regulators of blood glucose. Recall that they have opposing actions.
Insulin's job is to lower high blood sugar by promoting glucose storage (glycogenesis). Glucagon's job is to raise low blood sugar by promoting glucose release (glycogenolysis).

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 3 pp. 5-7, 6-8