Which factor is a known cause of hypercalcemia in patients taking thiazides?

• A. Chronic renal failure
• B. Malignancy
• C. Drug-induced hyperparathyroidism
• D. Thiazide diuretics

Answer: (D)

Thiazide diuretics are indeed known to cause hypercalcemia in patients who are taking them. The mechanism behind this involves the way thiazide diuretics function. Thiazides promote the reabsorption of calcium in the distal convoluted tubule of the nephron. As they inhibit sodium reabsorption, they simultaneously enhance calcium reabsorption, leading to increased calcium levels in the bloodstream. This can result in hypercalcemia, especially in patients who may already have predispositions or disturbances in calcium metabolism.

While chronic renal failure and malignancy are recognized causes of hypercalcemia, they are not directly related to the effects of thiazide diuretics. Drug-induced hyperparathyroidism is also a potential cause of elevated calcium levels, but this condition is not primarily associated with thiazide use. Therefore, understanding the specific role of thiazide diuretics in modifying calcium dynamics helps clarify why they are identified as a direct cause of hypercalcemia in this context.