ABSTRACT Objective: To assess the effect of bariatric surgical treatment of morbid obesity on bone mineral metabolism. Methods: We analyzed pertinent vitamin D and calci- um metabolic variables in 136 patients who had under- gone a malabsorptive bariatric operation. Measurements of bone mineral density (BMD), serum 25-hydroxyvita- min D (25-OHD), 1,25-dihydroxyvitamin D [1,25- (OH) 2 D], parathyroid hormone (PTH), calcium, phosphorus, and alkaline phosphatase were performed. Statistical analyses assessed correlations among various factors. Results: The mean age (±SD) of the study group was 48.34 ± 10.28 years. Their mean weight loss was 114.55 ± 45.66 lb, and the mean duration since the bariatric surgi- cal procedure was 54.02 ± 51.88 months. Seventeen patients (12.5%) had a T-score of -2.5 or less, and 54 patients (39.7%) had a T-score between -1.0 and -2.5. Of 119 patients in whom serum 25-OHD was measured, 40 (34%) had severe hypovitaminosis D (25-OHD <8 ng/mL), and 50 patients (42%) had low hypovitaminosis D (serum 25-OHD 8 to 20 ng/mL). The magnitude of weight loss correlated negatively with serum 25-OHD, calcium, phosphorus, and calcium × phosphorus product values and positively with serum alkaline phosphatase level. Serum 25-OHD and calcium concentrations corre- lated positively with the BMD. PTH, serum 1,25-(OH) 2 D, and alkaline phosphatase concentrations correlated nega- tively with the BMD, a reflection of the presence of sec- ondary hyperparathyroidism, an accelerated conversion of 25-OHD to 1,25-(OH) 2 D by the elevated PTH levels, and increased osteoblastic activity. The mean daily vitamin D supplementation was 6,472 ± 9,736 IU. Conclusion: Hypovitaminosis D and subsequent bone loss are common in patients who have undergone a bariatric surgical procedure for morbid obesity. These patients require rigorous vitamin D supplementation. (Endocr Pract. 2007;13:131-136) INTRODUCTION The effect of vitamin D and calcium deficiency on bone mineral metabolism after surgically induced malab- sorption for treatment of morbid obesity has not been fully addressed. Hypovitaminosis D is believed to be uncom- mon in the United States because of the vitamin D fortifi- cation of milk and other food products. Nevertheless, stud- ies have shown that lack of exposure to sunlight in certain geographic areas such as Great Britain, Canada, and the northern United States, in certain ethnic groups that are deprived of adequate exposure to sunlight, and in morbid- ly obese subjects who are housebound can lead to clinical hypovitaminosis D (1-5). More dramatic vitamin D deple- tion occurs in patients with intestinal malabsorption due to sprue, Crohn’s disease, and pancreatic insufficiency (6-8). Patients who undergo a bariatric surgical procedure for morbid obesity are more susceptible to acute depletion of their vitamin D stores and are likely to manifest the con- sequences of hypovitaminosis D and osteomalacia (9-13). Our study of 136 random patients who had undergone a malabsorptive bariatric operation demonstrates these abnormalities. PATIENTS AND METHODS Study Cohort Between 1983 and 2003, 136 patients were seen in our endocrinology center after they had undergone a bariatric surgical procedure for treatment of morbid obesi- ty. These patients were referred to us by 3 surgeons. Of these patients, 90% were referred by 1 surgeon, who ABNORMALITIES OF VITAMIN D AND CALCIUM METABOLISM AFTER SURGICAL TREATMENT OF MORBID OBESITY: A STUDY OF 136 PATIENTS Ali A. Abbasi, MD, FACP, FACE, 1 Mohammad Amin, MD, 1 Jacquelyn K. Smiertka, RN, 1 George Grunberger, MD, FACE, 1 Bruce MacPherson, MD, 2 Mustafa Hares, MD, 2 Marek Lutrzykowski, MD, 2 and Ali Najar, MD 2 Submitted for publication May 18, 2005 Accepted for publication August 30, 2006 From the 1 Grunberger Diabetes Institute, Bloomfield Hills, Michigan, and 2 St. Joseph Mercy Hospital, Pontiac, Michigan. Address correspondence and reprint requests to Dr. Ali A. Abbasi, P.O. Box 485, Highland, MI 48357. © 2007 AACE. ENDOCRINE PRACTICE Vol 13 No. 2 March/April 2007 131 Original Article Abbreviations: BMD = bone mineral density; DEXA = dual-energy x- ray absorptiometry; 1,25-(OH) 2 D = 1,25-dihydroxyvi- tamin D; 25-OHD = 25-hydroxyvitamin D; PTH = parathyroid hormone