A 28-year-old woman with newly diagnosed systemic sarcoidosis presents with fatigue and polyuria. Vital signs: BP 118/76, HR 88, RR 16, Temp 37.2°C, SpO₂ 98%. Laboratory studies reveal serum calcium 12.1 mg/dL, 24-hour urine calcium 420 mg/24h, PTH 8 pg/mL (normal 15-65), and 1,25-dihydroxyvitamin D 156 pg/mL (normal 19-67). Chest radiograph shows hilar lymphadenopathy. Which mechanism best explains her hypercalcemia?
- A)Impaired renal excretion of calcium due to interstitial nephritis
- B)Extrarenal conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by activated macrophages in granulomasGABARITO
- C)PTH-mediated increased renal tubular reabsorption of calcium
- D)PTHrP secretion from sarcoid granulomas stimulating bone resorption
- E)Direct osteoclast activation by TNF-alpha produced by T cells
Explicação
Sarcoid granulomas contain activated macrophages that express 1α-hydroxylase, producing calcitriol independently of PTH regulation. The elevated 1,25-dihydroxyvitamin D increases intestinal calcium absorption and bone resorption, causing hypercalcemia. PTH is ... Ver explicação completa e trilha adaptativa →