What is the most common cause of hypercalcemia?

What is the most common cause of hypercalcemia?

• A. Primary hyperparathyroidism
• B. Thiazide diuretics
• C. Hyperthyroidism
• D. Lymphoma

Answer: (A)

The main idea is that excess parathyroid hormone from the parathyroid glands is the most common cause of high calcium in adults. In primary hyperparathyroidism, usually due to a parathyroid adenoma, PTH levels rise inappropriately in the face of elevated calcium. This boosts calcium in three ways: it increases bone breakdown, enhances calcium reabsorption in the kidneys, and promotes production of active vitamin D that raises intestinal calcium absorption. Because of these combined effects, calcium levels rise more often and more reliably than with other conditions. Thiazide diuretics can nudge calcium upward by reducing its excretion, but they are not the usual or primary driver of hypercalcemia in most people. Hyperthyroidism can cause increased bone turnover and may lead to elevated calcium, but sustained hypercalcemia is not typical. Lymphoma can cause hypercalcemia through PTH-related peptide or vitamin D activation, but this is less common than primary hyperparathyroidism in the general population.

The main idea is that excess parathyroid hormone from the parathyroid glands is the most common cause of high calcium in adults. In primary hyperparathyroidism, usually due to a parathyroid adenoma, PTH levels rise inappropriately in the face of elevated calcium. This boosts calcium in three ways: it increases bone breakdown, enhances calcium reabsorption in the kidneys, and promotes production of active vitamin D that raises intestinal calcium absorption. Because of these combined effects, calcium levels rise more often and more reliably than with other conditions.

Thiazide diuretics can nudge calcium upward by reducing its excretion, but they are not the usual or primary driver of hypercalcemia in most people. Hyperthyroidism can cause increased bone turnover and may lead to elevated calcium, but sustained hypercalcemia is not typical. Lymphoma can cause hypercalcemia through PTH-related peptide or vitamin D activation, but this is less common than primary hyperparathyroidism in the general population.