Primary Hyperparathyroidism

A 62-year-old woman is found on routine laboratory testing to have a serum calcium level of 10.8 mg per deciliter (2.7 mmol per liter) (normal range, 8.4 to 10.4 [2.1 to 2.7]). The serum intact parathyroid hormone (PTH) concentration is 70 pg per milliliter (normal range, 15 to 75). Her history is notable only for hypertension that is well controlled with an angiotensin-receptor blocker; there is no history of kidney stones or fractures. Her family history is negative for hypercalcemia or endocrine tumors. Her 24-hour urinary calcium and creatinine levels are 280 mg and 1050 mg, respectively, and the ratio of calcium to creatinine clearance is 0.025. Bone densitometry shows T scores at the lumbar spine of -1.8, at the total hip of -2.2, and at the distal third of the radius of -3.0. How should she be further evaluated and treated?