Which of the following is NOT a listed cause of hypercalcemia?

• A. Parathyroid hormone excess
• B. Milk-alkali syndrome
• C. Immobilization
• D. Hypothyroidism

Answer: (D)

Hypercalcemia usually stems from either too much PTH activity or from processes that push calcium out of bone or increase its absorption. When PTH is excessive, calcium rises because bone resorption increases, renal reabsorption of calcium goes up, and production of active vitamin D is enhanced. Milk-alkali syndrome is a classic iatrogenic cause where large intake of calcium (often with alkali) leads to high calcium levels, metabolic alkalosis, and renal effects. Immobilization increases bone resorption due to lack of mechanical loading, releasing calcium into the bloodstream.

Hypothyroidism does not typically raise calcium levels and isn’t considered a cause of hypercalcemia, so it’s the exception here.