Charles J Keith, MD, Lauren Goss, MSPH, Allison A Gullick, MSPH, Britney L Corey, MD, Richard Stahl, MD, Jayleen Grams, MD, PhD. University of Alabama at Birmingham
INTRODUCTION: The effects of bariatric surgery on calcium, vitamin D, and parathyroid hormone (PTH) homeostasis have demonstrated conflicting results after short-term follow-up. The purpose of this study was to analyze outcomes of calcium, vitamin D, and PTH after bariatric surgery and compare the effects of Roux-en-Y gastric bypass (RYGB) with laparoscopic sleeve gastrectomy (LSG).
METHODS: All patients who underwent RYGB or LSG at a single institution over a 3-year period were identified from a prospectively maintained database. Subgroup analyses were performed stratifying by bariatric procedure. Patients with incomplete pre- and post-op values for a specific lab were excluded from analysis of that lab but were included in analyses of other lab values for which their information was complete. Vitamin D insufficiency was defined as <30 ng/mL, vitamin D deficiency as <20, and hyperparathyroidism as PTH>90 pg/mL. Bivariate frequencies were compared using Chi-square and Student’s t-test. Significance was p<0.05.
RESULTS: Of 195 patients who met inclusion criteria, 111 had RYGB and 84 had LSG. Pre-operative demographics were similar between the groups. Overall, a decrease in serum calcium (p=0.016), increase in PTH (p<0.001) and hyperparathyroidism (p=0.006), an increase in serum vitamin D (p<0.001), and improvement in vitamin D insufficiency (p=0.006) and deficiency (p=0.029) were seen post-operatively. RYGB patients showed improvement in serum vitamin D (p=0.002) and vitamin D insufficiency (p=0.010) but with increased PTH (p<0.001) and hyperparathyroidism (p=0.023) after operation. LSG patients had increased serum vitamin D (p=0.042) without significantly reducing their rate of insufficiency or deficiency, and they saw a decrease in PTH (p<0.001) without significantly affecting hyperparathyroidism. In comparison of RYGB and LSG, %WL (p<0.001), ΔBMI (p<0.001), and final BMI (p=0.032) were superior for RYGB. Serum calcium was lower in RYGB patients (p=0.032), and prevalence of hyperparathyroidism was similar. Although only RYGB patients had significant reduction in vitamin D insufficiency, rates of insufficiency were similar between groups, and deficiency was significantly more prevalent after RYGB than after LSG (p=0.045). There were no significant differences in follow up and supplement compliance.
CONCLUSIONS: RYGB and LSG have varying effects on calcium, vitamin D, and PTH. Although RYGB patients enjoy greater improvement in vitamin D insufficiency, they are at increased risk of deficiency in comparison to LSG patients. This may be due to malabsorption not inherent in LSG. Future studies are needed to determine how these changes impact skeletal health.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 80815
Program Number: P563
Presentation Session: Poster (Non CME)
Presentation Type: Poster