In hyperparathyroidism, how are calcium and phosphate levels typically affected?

In hyperparathyroidism, how are calcium and phosphate levels typically affected?

• A. Ca increased, P decreased
• B. Ca decreased, P increased
• C. Ca increased, P increased
• D. Ca decreased, P decreased

Answer: (A)

In hyperparathyroidism, excess parathyroid hormone drives calcium up and phosphate down. PTH increases serum calcium through three main routes: it stimulates bone resorption releasing calcium into the bloodstream, it enhances renal reabsorption of calcium, and it increases production of active vitamin D, which boosts intestinal calcium absorption. At the same time, PTH decreases phosphate reabsorption in the kidney’s proximal tubule, causing phosphate to be excreted and lowering serum phosphate. The net effect is hypercalcemia with hypophosphatemia, which is the typical pattern seen in primary hyperparathyroidism. (Note: in secondary hyperparathyroidism—often from chronic kidney disease—calcium may be low or normal and phosphate is usually high.)

In hyperparathyroidism, excess parathyroid hormone drives calcium up and phosphate down. PTH increases serum calcium through three main routes: it stimulates bone resorption releasing calcium into the bloodstream, it enhances renal reabsorption of calcium, and it increases production of active vitamin D, which boosts intestinal calcium absorption. At the same time, PTH decreases phosphate reabsorption in the kidney’s proximal tubule, causing phosphate to be excreted and lowering serum phosphate. The net effect is hypercalcemia with hypophosphatemia, which is the typical pattern seen in primary hyperparathyroidism. (Note: in secondary hyperparathyroidism—often from chronic kidney disease—calcium may be low or normal and phosphate is usually high.)