CKD-Mineral Bone Disorder and Anemia

A 52-year-old man with CKD stage 4 (eGFR 22 mL/min/1.73m²) due to diabetic nephropathy presents with fatigue and dyspnea on exertion. Hemoglobin is 8.2 g/dL, MCV 78 fL, serum iron 45 µg/dL (normal 60–170), ferritin 320 ng/mL (normal 30–300), and TSAT 18% (normal 20–50%). Reticulocyte count is 0.8% (normal 0.5–2.5%). Serum creatinine is 3.8 mg/dL, calcium 7.8 mg/dL (corrected), phosphate 5.2 mg/dL, and iPTH 285 pg/mL (normal 15–65). What is the primary mechanism responsible for the anemia in this patient?

A 52-year-old man with Stage 4 CKD (eGFR 22 mL/min/1.73m²) presents with bone pain and muscle weakness. Serum calcium is 7.8 mg/dL, phosphate 5.2 mg/dL, and alkaline phosphatase is elevated. Which investigation is most appropriate to confirm the type of renal osteodystrophy?

A 48-year-old woman with Stage 3b CKD presents with fatigue and dyspnea on exertion. Hemoglobin is 9.2 g/dL. Serum creatinine is 2.1 mg/dL, iron studies show serum iron 45 µg/dL, ferritin 180 ng/mL, and TSAT 18%. Which investigation is most appropriate to confirm the primary cause of anemia in this patient?

A 52-year-old man with CKD stage 4 (eGFR 28 mL/min/1.73m²) presents for routine follow-up. Serum calcium is 7.8 mg/dL (normal 8.5–10.5), phosphate 5.2 mg/dL (normal 2.5–4.5), and PTH 312 pg/mL (normal 15–65). Alkaline phosphatase is 78 U/L. He is asymptomatic. He is not on any phosphate binders or vitamin D supplements. What is the most appropriate next step in management?

A 52-year-old man with CKD stage 4 (eGFR 22 mL/min/1.73m²) presents with bone pain and muscle weakness. Laboratory investigations show: serum calcium 7.2 mg/dL, phosphate 5.8 mg/dL, alkaline phosphatase 120 U/L, PTH 680 pg/mL. Bone biopsy reveals high bone turnover with increased osteoblastic and osteoclastic activity. Which feature best distinguishes secondary hyperparathyroidism-induced high-turnover bone disease from adynamic bone disease in CKD?