**Core Concept**
Adipose tissue plays a crucial role in lipid metabolism, releasing free fatty acids into the circulation in response to hormonal signals. This process is essential for providing energy to various tissues, particularly the liver and muscles.

**Why the Correct Answer is Right**
The release of free fatty acids from adipose tissue is mediated by the hormone **hormone-sensitive lipase (HSL)**. HSL is activated by **cAMP** and **protein kinase A (PKA)**, which phosphorylate and activate the enzyme. This leads to the breakdown of triglycerides in adipocytes, resulting in the release of free fatty acids into the bloodstream. The free fatty acids are then transported to the liver, where they can be either oxidized for energy or esterified into very-low-density lipoproteins (VLDL) for storage and transport.

**Why Each Wrong Option is Incorrect**
**Option A:** This is a distractor, as the release of free fatty acids from adipose tissue is not primarily regulated by **insulin**. Insulin actually inhibits the release of free fatty acids by promoting the storage of triglycerides in adipocytes.
**Option B:** While **norepinephrine** can stimulate the release of free fatty acids from adipose tissue, it is not the primary regulator. Norepinephrine acts through **β-adrenergic receptors** to activate HSL, but this is a secondary response.
**Option C:** **Thyroid hormone** can influence lipid metabolism, but it is not directly involved in the release of free fatty acids from adipose tissue.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation is that the administration of **glucagon** can stimulate the release of free fatty acids from adipose tissue, which is why glucagon is used as a diagnostic test to assess the functioning of the adrenal glands.

**Correct Answer:** D.