A 33-year-old woman comes to the office for evaluation of hypercalcemia. Her Serum calcium was 12.1mg/dl on routine laboratory testing performed for a life insurance application. The patient feels well and has had no excessive urination, bone pain, abdominal pain, headache or constipation. Medical history is significant for upper gastrointestinal hemorrhage secondary to a gastric ulcer a year ago, for which she is on oral proton pump inhibitor. She has a 10-pack-year smoking history but does not use alcohol or illicit drugs. The patient’s menstrual cycles are regular; she has never been pregnant, is sexually active with one partner, and uses barrier contraception to prevent pregnancy. The patient’s mother underwent parathyroid surgery for symptomatic hypercalcemia and takes a pill twice a day for an unspecified pituitary tumor. Blood pressure is 120/80 mm Hg and pulse is 78/min. BMI is 27 kg/m2. Neck examination is unremarkable. A few small subcutaneous lipomas are present on the patient’s back. The rest of her physical examination is unremarkable. Laboratory results are as follows:
Calcium: 12 mg/dl
Phosphorus: 1.9 mg/dl
Creatinine: 0.8 mg/dl
Parathyroid hormone: 100 pg/ml (normal 10-65 pg/ml)
25-hydroxyvitamin D: 31 ng/ml (normal: 30-50 ng/ml)
24-hour urine calcium: 415 mg
Bone mineral density by DEXA is normal.