Which of the following is not listed as a cause of hypercalcemia?

• A. Hyperthyroidism
• B. Primary hyperparathyroidism
• C. Malignancy
• D. Excess vitamin D

Answer: (A)

Hypercalcemia typically arises from three broad mechanisms: increased bone resorption driven by excess parathyroid hormone (as in primary hyperparathyroidism), increased intestinal calcium absorption driven by excess vitamin D, and calcium release from bone or other sources in malignancy. Among the options, excess vitamin D and malignancy are classic, well-established causes, and primary hyperparathyroidism is the most common cause of hypercalcemia overall. Hyperthyroidism, while it can slightly raise calcium levels due to increased bone turnover, is not a standard listed cause of hypercalcemia in most references. Its effect on calcium is usually milder and not considered a primary etiologic category, so it’s not included among the typical causes.