All of the following are causes of hypercalcemia ‘except-
**Core Concept**
Hypercalcemia is a condition characterized by elevated serum calcium levels, which can result from various pathophysiological mechanisms. The causes of hypercalcemia can be broadly classified into four categories: hyperparathyroidism, malignancy, vitamin D intoxication, and other miscellaneous causes such as sarcoidosis, familial hypocalciuric hypercalcemia, and certain medications.
**Why the Correct Answer is Right**
To determine the correct answer, we need to evaluate each option and identify the causes of hypercalcemia. **Option A:** is a potential cause of hypercalcemia, as it is associated with excessive parathyroid hormone (PTH) production, leading to increased bone resorption and calcium release into the bloodstream. **Option B:** is also a known cause of hypercalcemia, as it can lead to increased vitamin D levels, enhancing calcium absorption from the gut. **Option C:** can cause hypercalcemia due to the increased production of 1,25-dihydroxyvitamin D, which stimulates calcium absorption from the gut.
**Why Each Wrong Option is Incorrect**
* **Option D:** is actually a cause of hypocalcemia, not hypercalcemia. It is associated with the release of phosphate from bones, which binds to calcium in the bloodstream, reducing its level.
**Clinical Pearl / High-Yield Fact**
Familial hypocalciuric hypercalcemia (FHH) is a genetic disorder characterized by elevated serum calcium levels, but with a key distinguishing feature: patients with FHH have a low fractional excretion of calcium in the urine (<0.01). This is in contrast to primary hyperparathyroidism, where patients typically have a high fractional excretion of calcium.
**Correct Answer:** D. Hypophosphatemia. Hypophosphatemia is a cause of hypocalcemia, not hypercalcemia.