A 65-year-old man presents with a 1-day history of hematuria and sharp flank pain (rated 10 of 10) radiating toward the groin on the right side.

[Kathryn]

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A 65-year-old man presents with a 1-day history of hematuria and sharp flank pain (rated 10 of 10) radiating toward the groin on the right side. Past medical history is significant for three prior episodes of nephrolithiasis over the past 5 years, all of which presented with a similar clinical picture. He is not taking any medication. There is no family history of renal calculi, renal disease, or endocrine disorders. His temperature is 36.9°C (98.5°F), heart rate is 125/ min, and blood pressure is 132/86 mm Hg. He is in obvious distress and cannot sit still on the bed. Physical examination is significant for a soft, nontender abdomen and extreme costovertebral angle tenderness on the right. Laboratory values show:
Na+: 142 mEq/L
K+: 4.8 mEq/L
Cl−: 104 mEq/L
HCO3−: 24 mEq/L
Ca2+ : 11.0 mg/dL
PO4: 1.4 mg/dL
Mg2+: 2.0 mg/dL
Blood urea nitrogen: 12 mg/dL
Creatinine: 1.0 mg/dL
Glucose: 118 mg/dL
Intact parathyroid hormone: 300 pg/mL
Which of the following is the most likely diagnosis?
(A) Malignancy
(B) Milk-alkali syndrome
(C) Primary hyperparathyroidism
(D) Sarcoidosis
(E) Secondary hyperparathyroidism