Which hormone stimulates lipolysis

KGMU 2024

Biochemistry & Nutrition

Medium

Appeared in: KGMU 2024

Explanation

Epinephrine, the 'fight-or-flight' hormone released during stress or exercise, is a potent stimulator of lipolysis.
It binds to beta-adrenergic receptors on adipocytes (fat cells), triggering a signaling cascade involving cyclic AMP (cAMP).
This cascade activates hormone-sensitive lipase (HSL), the key enzyme that breaks down stored triglycerides into free fatty acids and glycerol.
The released free fatty acids serve as a crucial energy source for the body during times of high demand.

Option A: While glucagon does stimulate lipolysis, particularly during fasting, its primary and more potent physiological role is to increase blood glucose levels by acting on the liver.
Option C: Ptyalin, also known as salivary amylase, is a digestive enzyme, not a hormone. Its function is to begin the digestion of carbohydrates (starches) in the mouth.
Option D: Oxytocin is a hormone primarily involved in stimulating uterine contractions during labor and milk ejection during lactation. It has no direct role in fat metabolism or lipolysis.

Visual 1: Diagram - A flowchart illustrating the mechanism of epinephrine-stimulated lipolysis. It would show epinephrine binding to a beta-adrenergic receptor on an adipocyte, the activation of adenylyl cyclase, the increase in cAMP, the activation of Protein Kinase A, and the subsequent phosphorylation and activation of Hormone-Sensitive Lipase (HSL) to break down triglycerides.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal Regulation of Metabolism as background academic context rather than a clinical decision trigger.
Understanding the hormonal control of lipolysis is fundamental for nurses managing patients with metabolic disorders like obesity, metabolic syndrome, and diabetes, where this process is often dysregulated.
In critically ill patients, the high levels of stress hormones like epinephrine can cause excessive lipolysis, leading to hyperlipidemia, which can complicate patient management.
What if? If a patient is taking a non-selective beta-blocker (e.g., propranolol), the lipolytic response to epinephrine will be blunted. This can impair their ability to mobilize energy during stress and may mask some of the warning signs of hypoglycemia.

How to Approach the Question

First, identify the key process in the question: 'lipolysis,' which is the breakdown of fat for energy.
Second, systematically review the function of each hormone listed in the options.
Third, eliminate options with clearly unrelated functions. Ptyalin is a digestive enzyme, and Oxytocin is related to childbirth and lactation.
Fourth, compare the remaining options, Glucagon and Epinephrine. Both stimulate lipolysis, so you must differentiate their primary roles. Recall that epinephrine is the 'fight-or-flight' hormone that rapidly mobilizes energy stores.
Finally, select Epinephrine as the most potent and direct stimulator of lipolysis in response to acute stress among the choices provided.

Concept Tested & Keywords

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