In primary hyperparathyroidism, which pattern is typically observed for serum calcium and phosphate?

In primary hyperparathyroidism, which pattern is typically observed for serum calcium and phosphate?

• A. Elevated calcium with decreased phosphate
• B. Elevated calcium with increased phosphate
• C. Decreased calcium with decreased phosphate
• D. Normal calcium with normal phosphate

Answer: (A)

In primary hyperparathyroidism, there is too much parathyroid hormone, which pushes calcium up and phosphate down in the blood. PTH raises calcium by increasing bone resorption, enhancing renal calcium reabsorption, and boosting intestinal calcium absorption through activated vitamin D. At the same time, PTH causes the kidneys to excrete more phosphate, reducing serum phosphate levels. The net result is higher calcium with lower phosphate. The other patterns don’t fit because they would require different PTH activity: without excess PTH, calcium wouldn’t be up, and phosphate wouldn’t be appropriately low.

In primary hyperparathyroidism, there is too much parathyroid hormone, which pushes calcium up and phosphate down in the blood. PTH raises calcium by increasing bone resorption, enhancing renal calcium reabsorption, and boosting intestinal calcium absorption through activated vitamin D. At the same time, PTH causes the kidneys to excrete more phosphate, reducing serum phosphate levels. The net result is higher calcium with lower phosphate. The other patterns don’t fit because they would require different PTH activity: without excess PTH, calcium wouldn’t be up, and phosphate wouldn’t be appropriately low.