Bone Abstracts

Vitamin D deficiency is common in older persons and non-western immigrants. Vitamin D is often started in loading doses of 50 000 IU/ml solution. Though, generally considered safe, this highly concentrated solution carries some risks as is illustrated by the following cases. A woman of >80 years old was admitted with hypercalcemia, calcium 3.27 mmol/l. She complained of nausea, thirst and polyuria for 3 months. History included cholecystitis, atrial fibrillation, myocardial infarction, type 2 diabetes, pyelonephritis, and moderate renal insufficiency (preexisting creatinine 213 μmol/l). Medication included tolbutamide, pantoprazol, and metoprolol. Physical exam was unremarkable except for a 3/6 systolic murmur. Laboratory data included an ESR of 69 mm, phosphate 1.1 mmol/l, albumin 34 g/l, creatinin 254 μmol/l, alkaline phosphatase 95 U/l. The patient was rehydrated with saline and received pamidronate i.v. Skeletal radiographs showed osteoarthritis of both hips, but no osteolytic lesions. The abdominal ultrasound and mammography did not reveal a cause for the hypercalcemia. Protein electrophoresis did not show an M-protein. PTH was 4.2 pmol/l, 25(OH)D was 575 nmol/l (ref 50–200), 1,25(OH)2D was 115 pmol/l (ref 50–160). Vitamin D intoxication was diagnosed. The patient had used 50 000 IU vitamin D3 daily for 3 months, but this was not on the medication list. Serum calcium normalized after prednisone 20 mg/day. An additional case occurred in an 27-year-old woman of Moroccan descent who had a level of 430 nmol/l after using daily 50 000 IU for 6 weeks. Her serum calcium was normal. A very high serum 25(OH)D was measured, 961 and 624 nmol/l respectively in two participants of the Longitudinal Aging Study Amsterdam, also using a highly concentrated solution. The highly concentrated vitamin D3 solution of 50 000 IU/ml may easily cause vitamin D intoxication when dosing errors are made. A less concentrated vitamin D solution would be advisable for loading dose.