A 72-year-old man with severe COPD exacerbation presents with dyspnea, hypoxemia (SpO2 88%), and tachycardia (HR 112). Laboratory studies reveal serum calcium 4.2 mg/dL, phosphate 6.8 mg/dL, and PTH 180 pg/mL. Notably, serum magnesium is 1.1 mg/dL (normal 1.7–2.2 mg/dL). He denies recent diuretic use. Chest X-ray confirms acute infiltrates without infiltrative disease. Which mechanism best explains his resistant hypocalcemia unresponsive to PTH?
- A)Calcitonin excess from lung malignancy
- B)Acute phosphate poisoning
- C)Primary hypoparathyroidism
- D)Hypomagnesemia impairing PTH secretion and actionGABARITO
- E)Vitamin D deficiency alone
Explicação
Hypomagnesemia suppresses PTH secretion and impairs end-organ PTH receptor responsiveness. Despite elevated PTH, magnesium depletion prevents adequate correction of hypocalcemia. Correction requires magnesium replacement alongside calcium. Ver explicação completa e trilha adaptativa →