**Core Concept**
Acanthosis nigricans is a skin condition characterized by dark, velvety skin patches, typically in the folds and creases of the body. It is often associated with insulin resistance, obesity, and other endocrine disorders. The condition is thought to be caused by increased insulin levels, which stimulate the growth of skin cells.

**Why the Correct Answer is Right**
The correct answer is associated with a medication that increases insulin levels or causes insulin resistance. This medication acts by inhibiting the enzyme glucagon-like peptide-1 (GLP-1) receptor, leading to increased glucose levels and insulin resistance. As a result, the skin condition acanthosis nigricans develops.

**Why Each Wrong Option is Incorrect**
**Option A:** This medication is not typically associated with insulin resistance or acanthosis nigricans.
**Option B:** This medication is actually used to treat diabetes by increasing insulin sensitivity, not causing insulin resistance.
**Option C:** This medication is not commonly linked to acanthosis nigricans, though it may cause other skin reactions.

**Clinical Pearl / High-Yield Fact**
Insulin resistance is a common underlying cause of acanthosis nigricans, and it can also be a precursor to type 2 diabetes.

**Correct Answer:** C. Pioglitazone, a thiazolidinedione, can cause insulin resistance and lead to acanthosis nigricans.