You are answering a USMLE-style medical question. Question: Two hours after admission to the hospital for dialysis, a 63-year-old woman has severe pain in her lower back. The pain is 8 out of 10 in intensity and radiates down the legs. She underwent a laparoscopic cholecystectomy 4 years ago. She has hypertension, chronic kidney disease, type 2 diabetes mellitus, and major depressive disorder. She lives with her daughter and reports frequent fights with her at home. Her current medications include sertraline, insulin, enalapril, sodium bicarbonate, and sevelamer. She appears uncomfortable. Her temperature is 37.3°C (99.1°F), pulse is 102/min, respirations are 15/min, and blood pressure is 132/94 mm Hg. There is severe tenderness on palpation over the L2 vertebra; range of motion is limited. Neurologic examination shows no focal findings. Laboratory studies show: Hemoglobin 10.1 g/dL Leukocyte count 8,700/mm3 Platelet count 130,000/mm3 Serum Na+ 136 mEq/L Cl- 101 mEq/L K+ 5.1 mEq/L Calcium 8.2 mg/dL Urea nitrogen 33 mg/dL Glucose 190 mg/dL Creatinine 3.8 mg/dL An x-ray of the spine shows a wedge compression fracture of the L2 vertebra. Which of the following is the most likely explanation for these findings?" Options: A) Tertiary hyperparathyroidism B) Secondary hyperparathyroidism C) Elder abuse D) Primary hyperparathyroidism Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.