3Serum calcium 11.0 with phosphate 5.5 — combined risk of metastatic calcification✓ Correct answer
4Serum albumin 3.8 g/dL — suggests malnutrition could worsen hyperparathyroidism
Explanation
Correct (2): Calcitriol (active vitamin D) suppresses PTH but raises Ca and phosphate; hypercalcemia and hyperphosphatemia together raise Ca×P product → metastatic calcification (vasculature, soft tissue). Hold calcitriol when Ca >10.5 or Ca×P >55. (1) Indication for treatment. (3,4) Unrelated.
In-depth explanation
Memory Tip Vit D analogs (calcitriol, paricalcitol, doxercalciferol) = "Watch Ca and P." Calcimimetic (cinacalcet, etelcalcetide) lowers PTH without raising Ca.
Clinical scenario
Scenario 62-year-old male CKD 4 on calcitriol 0.25 mcg PO daily. Routine labs: Ca 11.0, phosphate 5.5, PTH 220.
Key concepts
Calcitriol — Active vitamin D; suppresses PTH but raises Ca and P.
Ca×P product — Multiply Ca and P; >55 risks metastatic calcification.
Secondary hyperparathyroidism — CKD-related; treated with vit D analogs, calcimimetics, phosphate binders.