A 60-year-old man was seen after presenting to the emergency room with seizures. His history is notable for having had gastric bypass surgery 5 years ago for obesity. About 2 months before, he injured himself playing tennis. An x-ray did not show a fracture, but he was noted to have radiographic osteopenia. A bone density study by DXA was performed that revealed a L1-L4 T-score of -3.0, a total hip T-score of -2.2, femoral neck T-score of -2.4 and a 33% radius T-score of -3.6. He was started on a bisphosphonate and presented with seizures about 6 weeks later. His calcium was noted to be low at about 5.8 mg/dl with an ionized calcium of about 0.6 mmol/L. His PTH was high at about 450 pg/ml. His vitamin D level was less than 7 ng/ml. His creatinine was normal. Vitamin D therapy was started at 50,000 IU daily initially and titrated to keep his serum 25-OH vitamin D level in the range of 32-60 ng/ml. Calcium citrate was started and titrated to keep his calcium in the normal range.

Gastrectomy and gastric bypass procedures are commonly associated with increased bone turnover and low bone mass (1). Vitamin D and calcium malabsorption result in secondary hyperparathyroidism and a mixed picture of osteomalacia and osteoporosis (2, 3). Hypocalcemia is a contraindication to the use of bisphosphonates and bisphosphonates are not indicated for therapy of osteomalacia (bisphosphonate product inserts). In patients with vitamin D insufficiency or deficiency, bisphosphonates may cause hypocalcemia (4). Hypocalcemia has also been noted in patients with unrecognized celiac disease treated for low bone density with bisphosphonates (5). DXA studies are warranted in patients that have had gastric bypass or gastrectomy surgery (NOF Clinician Guide www.nof.org). In addition, a basic evaluation in patients being considered for osteoporosis therapy is recommended to exclude secondary contributing factors (NOF Clinician Guide www.nof.org). A serum calcium is necessary to exclude pre-existing hypocalcemia and a creatinine is necessary to ensure adequate renal function. A vitamin D level should be checked when osteomalacia or vitamin D insufficiency or deficiency is a consideration. Additional testing is recommended based on the clinical situation (NOF Clinician Guide). If bisphosphonates are indicated, then absorption problems or side effects related to the abnormal anatomy may make IV bisphosphonates more appropriate for many patients.

Appropriate guidelines for nutritional support in patients with bariatric surgery or gastrectomy are required. The American Association of Clinical Endocrinologists (AACE) - The Obesity Society (TOS) – American Society of Metabolic and Bariatric Surgery (ASMBS) Clinical Practice Guidelines for the Perioperative Nutritional, Metabolic and Nonsurgical Support of the Bariatric Surgery Patient has been developed to help meet this need (pending publication). Patients with a history of gastric bypass or gastrectomy should receive DXA studies to evaluate their bone status and appropriate evaluation for vitamin D and calcium insufficiency are necessary before consideration of bisphosphonate therapy. Consultation with an endocrinologist should be considered for patients being considered for “osteoporosis” therapy with a history of bariatric surgery or gastrectomy.