**Core Concept**
Hypercalcemia refers to an elevated calcium level in the blood, which can result from various physiological or pathological processes. The regulation of calcium levels is primarily controlled by parathyroid hormone (PTH) and vitamin D, which work together to maintain calcium homeostasis.

**Why the Correct Answer is Right**
To determine which option would not lead to hypercalcemia, we must consider the mechanisms underlying each choice. Hypercalcemia can occur due to increased bone resorption, increased absorption of calcium from the intestine, or decreased excretion of calcium in the urine. However, certain conditions may not lead to hypercalcemia.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because hyperparathyroidism is a condition characterized by an overproduction of parathyroid hormone (PTH), which stimulates bone resorption and increases calcium levels in the blood, leading to hypercalcemia.

**Option B:** This choice is incorrect because vitamin D toxicity can lead to increased absorption of calcium from the intestine, resulting in hypercalcemia.

**Option C:** This choice is incorrect because certain malignancies, such as multiple myeloma, can lead to hypercalcemia through the production of PTH-related protein (PTHrP) or by promoting bone resorption.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that hypercalcemia can be caused by a wide range of conditions, including hyperparathyroidism, vitamin D toxicity, and malignancies. It's essential to consider the clinical presentation and laboratory findings to determine the underlying cause.

**Correct Answer:** D.