Most common cause of Hyperparathyroidism is?
**Core Concept**
Hyperparathyroidism is characterized by the overproduction of **parathyroid hormone (PTH)**, leading to various clinical manifestations. The primary cause can be either primary, secondary, or tertiary hyperparathyroidism, each with distinct underlying mechanisms. Primary hyperparathyroidism is the most common form.
**Why the Correct Answer is Right**
The most common cause of primary hyperparathyroidism is a **parathyroid adenoma**, which is a benign tumor of one of the parathyroid glands, leading to excessive secretion of PTH. This condition accounts for about 80-85% of all primary hyperparathyroidism cases. The adenoma causes the parathyroid gland to become overactive, resulting in an excessive production of PTH.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, although **parathyroid hyperplasia** can cause primary hyperparathyroidism, it is less common than parathyroid adenoma.
**Option B:** Incorrect as **parathyroid carcinoma** is a rare cause of primary hyperparathyroidism.
**Option D:** Incorrect because **familial hypocalciuric hypercalcemia** is a rare genetic disorder causing hyperparathyroidism, not the most common cause.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that primary hyperparathyroidism due to a parathyroid adenoma typically presents with **hypercalcemia**, which can lead to symptoms such as kidney stones, bone pain, and neuropsychiatric symptoms.
**Correct Answer:** D. Parathyroid Adenoma.