**Core Concept**
Multiple Endocrine Neoplasia Type 1 (MEN-1) is a rare genetic disorder characterized by the occurrence of tumors in multiple endocrine glands, including the parathyroid glands, pituitary gland, and pancreas.

**Why the Correct Answer is Right**
MEN-1 is associated with hyperparathyroidism due to parathyroid gland tumors, leading to elevated calcium levels (hypercalcemia) in the blood. The elevated calcium levels can stimulate the parathyroid glands to produce even more parathyroid hormone (PTH). Elevated PTH levels can also lead to increased calcium absorption from the intestine, contributing to hypercalcemia.

**Why Each Wrong Option is Incorrect**
* **Option A:** Vanillylmandelic acid (VMA) in urine is a marker for pheochromocytoma, a tumor of the adrenal glands, which is more commonly associated with Multiple Endocrine Neoplasia Type 2 (MEN-2).
* **Option B:** Elevated calcitonin levels are associated with medullary thyroid carcinoma, a tumor of the thyroid gland, which is also more commonly associated with MEN-2.
* **Option C:** Hypergastrinemia (elevated gastrin levels) is associated with Zollinger-Ellison syndrome, a tumor of the pancreas or duodenum, which can be seen in MEN-1 but is not the most characteristic feature.
* **Option D:** Hyperprolactinemia (elevated prolactin levels) is associated with pituitary tumors, which can be seen in MEN-1, but is not the most characteristic feature of the syndrome.

**Clinical Pearl / High-Yield Fact**
MEN-1 is an autosomal dominant genetic disorder caused by mutations in the MEN1 gene, which encodes a protein involved in the regulation of gene expression. Patients with MEN-1 are at increased risk of developing hyperparathyroidism, pituitary tumors, and pancreatic tumors, and should be screened regularly for these conditions.

**Correct Answer:** C. Hypergastrinemia