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Medical Emergencies · single question

A patient's serum calcium is 14 mg/dL (normal 8.5–10.2 mg/dL). The most likely cause of this hypercalcemia is:

  1. Increased PTH production (primary hyperparathyroidism)
  2. Vitamin D deficiency
  3. Hypothyroidism
  4. Primary hyperthyroidism
Show answer and explanation

Correct answer: A. Increased PTH production (primary hyperparathyroidism)

  • A. Correct. The classic cause of chronic hypercalcemia is primary hyperparathyroidism — autonomous PTH oversecretion drives bone resorption and renal Ca reabsorption, raising serum calcium. (Malignancy is the other major cause.)
  • B. Vitamin D deficiency causes hypocalcemia, not hypercalcemia.
  • C. Hypothyroidism does not characteristically raise calcium.
  • D. Hyperthyroidism can mildly raise calcium but is not the classic cause of a value this high; increased PTH is the best answer.

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