Okay, let's tackle this question about the first response to hypoglycemia. The user wants a detailed explanation for an MCQ where the correct answer is the first response. First, I need to recall the body's immediate reaction when blood glucose drops.

Hypoglycemia triggers counter-regulatory hormones. The primary ones are glucagon and adrenaline. But which one comes first? I remember that alpha cells in the pancreas release glucagon in response to low blood sugar. However, if the hypoglycemia is severe, the sympathetic nervous system kicks in, releasing adrenaline from the adrenal medulla. But which is the very first response?

Wait, the body's first line of defense is the release of glucagon. Glucagon acts on the liver to break down glycogen into glucose via glycogenolysis. Adrenaline comes into play if glucagon isn't sufficient, perhaps after a delay. So the initial response is glucagon release. But I need to confirm this.

Alternatively, maybe the initial response is the sympathetic nervous system activation. But adrenaline is a hormone, and the sympathetic response is more about the fight-or-flight, which includes sweating, tremors, etc. However, the actual metabolic response to hypoglycemia would be glucagon first. So the first response is glucagon release from alpha cells.

Now, the options aren't provided, but the correct answer is the one that mentions glucagon. The other options might include adrenaline, insulin release, or something else. Let's structure the explanation accordingly.

Core Concept: The body's initial counter-regulatory response to hypoglycemia is the release of glucagon from pancreatic alpha cells to increase blood glucose via hepatic glycogenolysis.

Why correct: Glucagon acts on the liver to stimulate glycogenolysis and gluconeogenesis. Adrenaline is a secondary response if glucagon isn't enough. Insulin release would worsen hypoglycemia, so that's incorrect. Cortisol and growth hormone are slower responses.

Incorrect options: Adrenaline (Option B) is secondary. Insulin (Option C) is wrong because it lowers glucose. Cortisol (Option D) is a late response.

Clinical Pearl: Remember that glucagon is the first line, followed by adrenaline, then cortisol and growth hormone. This sequence is crucial for NEET and USMLE.

Now, putting this into the required sections with the correct structure and ensuring each part is concise and within the character limit.

**Core Concept**
The body's primary counter-regulatory response to hypoglycemia is the release of **glucagon** from pancreatic alpha cells, which stimulates hepatic glycogenolysis and gluconeogenesis to restore normoglycemia. This occurs before sympathetic nervous system activation (e.g., adrenaline release).

**Why the Correct Answer is Right**
Glucagon is the **first-line hormone** to counteract hypoglycemia. It acts on liver cells via **glucagon receptors**, activating **adenylate cyclase** to increase cAMP, which in turn activates **phosphorylase kinase** and **glycogen phosphorylase** to break down glycogen into glucose (glycogenolysis). Adrenaline (epinephrine) is a **secondary response**, released when glucagon alone is insufficient, particularly in severe hypoglycemia

✓ Correct Answer: B. Increased glucagon