Free nephrology board questions: Calcium Metabolism

A 37-year-old previously healthy man is referred for hypercalcemia; serum calcium has ranged from 10.7 to 11.3 mg/dL over the past year. He feels well, takes no medications, and is adopted, so family history is unknown. Examination is unremarkable. Creatinine is 0.7 mg/dL, calcium 11.2 mg/dL, intact PTH 64 pg/mL (10–65), 25-hydroxyvitamin D 35 ng/mL, and urine calcium-to-creatinine ratio 0.005 (<0.14). Kidney ultrasound is normal. What is the most likely cause of his hypercalcemia?

A 34-year-old woman presents with 3 days of nausea, vomiting, and confusion. She recently adopted an 'organic' lifestyle and has been taking large doses of over-the-counter calcium carbonate and vitamin D supplements. She was previously healthy except for hypothyroidism treated with levothyroxine. Labs: calcium 13.6 mg/dL, creatinine 2.3 mg/dL (baseline 0.8), and an arterial blood gas showing metabolic alkalosis (HCO3- 34 mEq/L); phosphate is low-normal and intact PTH is suppressed. Pregnancy test is negative. Which of the following is the most likely diagnosis?