A 36-year-old woman comes to the physician due to low back pain. The pain began 5 months ago and is getting progressively worse. She describes it as aching, non-radiating, and without any aggravating or relieving factors. The patient underwent Roux-en-Y gastric bypass surgery for morbid obesity 2 years ago, after which she lost about 45.4 kg (100 lb). She takes a daily multivitamin containing calcium (1200 mg elemental calcium) and vitamin D (400 IU of cholecalciferol). She eats a normal diet. Spinal examination shows no focal tenderness. Laboratory results are as follows: Bone mineral density, performed using dual-energy x-ray absorptiometry, reveals a T-score of -2.0 at the lumbar spine and -1.5 at the hip. Serum parathyroid hormone level is 955 pg/mL. Which of the following is the best next step in management of this patient?

Question

A 36-year-old woman comes to the physician due to low back pain.  The pain began 5 months ago and is getting progressively worse.  She describes it as aching, non-radiating, and without any aggravating or relieving factors.  The patient underwent Roux-en-Y gastric bypass surgery for morbid obesity 2 years ago, after which she lost about 45.4 kg (100 lb).  She takes a daily multivitamin containing calcium (1200 mg elemental calcium) and vitamin D (400 IU of cholecalciferol).  She eats a normal diet.  Spinal examination shows no focal tenderness.  Laboratory results are as follows:  Bone mineral density, performed using dual-energy x-ray absorptiometry, reveals a T-score of -2.0 at the lumbar spine and -1.5 at the hip.  Serum parathyroid hormone level is 955 pg/mL.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bedd_7f19_8f63_21a28a5e4518_MD0005_00 This patient, with back pain, low phosphorus level, high alkaline phosphatase, and history of bariatric surgery, has likely vitamin D deficiency, with osteomalacia and secondary hyperparathyroidism. Hypophosphatemia is common and may be present in patients with normal calcium levels (increased production of parathyroid hormone causes increased renal excretion of phosphorus while maintaining calcium at normal levels). Serum 25-hydroxyvitamin D level is a very sensitive indicator for vitamin D stores and should be measured in patients suspected of vitamin D deficiency. A level <20 ng/mL is diagnostic. Gastric bypass surgery causes some degree of malabsorption in a majority of patients. To prevent the development of deficiencies following a bariatric procedure, all patients need lifelong supplementation of vitamins (eg, B1, B12, folic acid, vitamin D) and minerals eg, (iron, calcium, trace minerals). Patients should receive at least 2000-3000 units of cholecalciferol (vitamin D3) per day to maintain vitamin D levels of 30-50 ng/mL, and some may require even higher doses. This patient's current dose (400 IU per day) is insufficient to maintain vitamin D levels following Roux-en-Y gastric bypass. (Choice B) Testing for stool fat can assess malabsorption but would not confirm the diagnosis of vitamin D deficiency. Patients with gastric bypass surgery should receive vitamin D supplementation assuming malabsorption, regardless of stool fat content. (Choice C) Zoledronic acid is indicated for treatment of osteoporosis in men and postmenopausal women and for Paget's disease of bone. It should not be used in patients with vitamin D deficiency or malabsorption syndromes due to the risk of hypocalcemia. (Choice D) Ultrasound of the neck is useful to detect parathyroid adenomas, the most common cause of primary hyperparathyroidism. However, vitamin D deficiency causes secondary hyperparathyroidism and ultrasound is not helpful. (Choice E) Mild to moderate hypophosphatemia due to vitamin D deficiency will correct spontaneously with treatment of the underlying disorder. Supplementation of phosphorus is not necessary. Educational objective: Gastric bypass bariatric surgery causes malabsorption in a majority of patients. Patients will require at least 2000-3000 IU/day of cholecalciferol (vitamin D3) to maintain normal vitamin D levels. Other vitamins (eg, B1, B12, folic acid) and minerals (eg, iron, calcium, trace minerals) should be supplemented as well. References: Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient--2013 update: cosponsored by American Association of Clinical Endocrinologists, the Obesity Society, and American Society for Metabolic & Bariatric Surgery. (http://www.ncbi.nlm.nih.gov/pubmed/23529351) Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. (http://www.ncbi.nlm.nih.gov/pubmed/21646368)

A 36-Year-Old Woman Comes to the Physician Due to Low