A 35-year-old man with stage 4 chronic kidney disease (GFR 18 mL/min/1.73m²) presents with bone pain and muscle cramps. Vital signs: BP 148/92, HR 88, RR 16, Temp 37°C. Labs show serum calcium 7.8 mg/dL, phosphate 6.2 mg/dL, PTH 620 pg/mL, and 25-hydroxyvitamin D 15 ng/mL. Intact parathyroids visualized on ultrasound. He denies recent fractures. Which pathophysiologic mechanism best explains his markedly elevated PTH?
- A)Increased sensitivity of parathyroid glands to FGF23 stimulation
- B)Primary defect in parathyroid hormone synthesis genes
- C)PTH-secreting adenoma unrelated to renal disease
- D)Autonomous parathyroid gland hyperfunction independent of calcium levels
- E)Decreased phosphate excretion leading to hyperphosphatemia and secondary hyperparathyroidismGABARITO
Explicação
Secondary hyperparathyroidism in CKD is driven by decreased phosphate excretion (hyperphosphatemia), hypocalcemia, and reduced renal conversion of 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D. Hyperphosphatemia directly stimulates PTH secretion and su... Ver explicação completa e trilha adaptativa →