Which laboratory finding would most suggest hyperparathyroidism as a cause of hypertension?

• A. Hypercalcemia
• B. Hyponatremia
• C. Hyperkalemia
• D. Hypophosphatemia

Answer: (A)

Elevated calcium in the blood points to primary hyperparathyroidism as a cause of hypertension. Excess parathyroid hormone raises serum calcium by increasing bone resorption, enhancing renal calcium reabsorption, and boosting intestinal calcium absorption via active vitamin D. The resulting hypercalcemia can increase vascular smooth muscle tone and peripheral resistance, contributing to higher blood pressure. While phosphate levels are often low due to renal phosphate wasting in hyperparathyroidism, this finding is less specific. Hyponatremia or hyperkalemia do not align with this condition. Thus, hypercalcemia best supports hyperparathyroidism as the cause of hypertension.