Hypercalcemia is seen in all except –
**Core Concept**
Hypercalcemia refers to elevated calcium levels in the blood, which can be caused by a variety of factors including hormonal imbalances, vitamin D excess, and bone disease. The body tightly regulates calcium levels through a complex interplay of hormones, including parathyroid hormone (PTH), calcitonin, and vitamin D.
**Why the Correct Answer is Right**
Hypercalcemia can occur in several clinical scenarios, including primary hyperparathyroidism, where excess PTH production leads to increased bone resorption and renal calcium reabsorption. Other causes include malignancy, particularly squamous cell carcinoma of the head and neck, which can produce parathyroid hormone-related protein (PTHrP) to stimulate osteoclast activity. Additionally, excessive intake of vitamin D or its analogs can also lead to hypercalcemia.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, while it may be a rare cause of hypercalcemia, it is not a common or well-known association. However, in the absence of more information, we can still eliminate it.
**Option B:** This option is incorrect because it is actually a common cause of hypercalcemia. Vitamin D excess can occur due to excessive supplementation or synthetic analogs.
**Option C:** This option is incorrect because it is a well-known cause of hypercalcemia, particularly in patients with advanced malignancy.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that hypercalcemia can have a wide range of causes, and a thorough investigation is necessary to identify the underlying etiology. A classic exam trap is to assume that primary hyperparathyroidism is the sole cause of hypercalcemia, when in fact other conditions, such as malignancy or vitamin D excess, may also be responsible.
**Correct Answer: None of the above.**