Excess vitamin D leads to which laboratory pattern?

• A. Ca high, Phosphate low, PTH high, Vitamin D normal
• B. Ca low, Phosphate high, PTH low, Vitamin D high
• C. Ca high, Phosphate high, PTH low, Vitamin D high
• D. Ca high, Phosphate normal, PTH high, Vitamin D normal

Answer: (C)

Excess vitamin D boosts absorption of calcium and phosphate from the gut and stimulates bone turnover, so both calcium and phosphate rise in the blood. The resulting hypercalcemia then suppresses the parathyroid hormone, so PTH falls. With vitamin D levels already elevated, you end up with high calcium, high phosphate, low PTH, and high vitamin D. This pattern specifically fits vitamin D intoxication.