The most common cause of hyperparathyroidism is ______.

• A. an adenoma
• B. Wilson disease
• C. accidental removal or damage of the parathyroid glands
• D. hypothyroidism

Answer: (A)

A parathyroid adenoma is the most common cause of hyperparathyroidism. A single benign tumor in one gland secretes PTH autonomously, raising calcium levels through increased bone resorption and enhanced renal calcium reabsorption, independent of the body’s calcium level. This autonomous PTH elevation leads to the hypercalcemia seen in the condition. Other options don’t fit: Wilson disease is a liver-related copper overload disorder with no direct role in parathyroid hormone regulation; accidental removal or damage to the parathyroids after surgery typically causes hypoparathyroidism with low PTH rather than hyperparathyroidism; hypothyroidism is a thyroid condition and does not cause elevated PTH. While less common causes include diffuse gland hyperplasia or, rarely, carcinoma, a solitary adenoma remains the most frequent culprit.