## **Core Concept**
Hypercalcemia can result from various conditions, including hyperparathyroidism, malignancy, vitamin D intoxication, and sarcoidosis. Corticosteroids are useful in treating hypercalcemia caused by certain conditions that are responsive to steroid therapy.

## **Why the Correct Answer is Right**
Sarcoidosis (**) is a condition where corticosteroids are a mainstay of treatment. Hypercalcemia in sarcoidosis is due to the overproduction of **1,25-dihydroxyvitamin D** by macrophages in granulomas, leading to increased intestinal absorption of calcium. Corticosteroids can reduce the formation of **1,25-dihydroxyvitamin D** and are therefore effective in lowering calcium levels in this context.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Hyperparathyroidism (**) is primarily treated by addressing the underlying cause, such as parathyroidectomy for primary hyperparathyroidism. While some cases may involve management of symptoms or consequences of hypercalcemia, corticosteroids are not the first-line treatment for hypercalcemia caused by hyperparathyroidism.
* **Option B:** Vitamin D intoxication (**) leads to hypercalcemia through increased intestinal absorption of calcium. Treatment involves stopping the vitamin D supplement, hydration, and sometimes bisphosphonates or glucocorticoids, but the condition is not as primarily responsive to corticosteroids as sarcoidosis.
* **Option C:** Familial hypocalciuric hypercalcemia (**) is a benign condition caused by mutations in the calcium-sensing receptor gene. It does not typically require treatment for hypercalcemia, as it is often asymptomatic.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that in cases of hypercalcemia, identifying the underlying cause is crucial for targeted therapy. For instance, **sarcoidosis-induced hypercalcemia** is uniquely responsive to corticosteroids, making it a critical diagnosis to consider.

## **Correct Answer:** D. Sarcoidosis.