Secondary Hyperparathyroidism, Bone Density and Bone Turnover After Bariatric Surgery: Differences Between Roux-en-Y Gastric Bypass and Sleeve Gastrectomy

Abstract

Introduction: Although malabsorption of nutrients and changes in intestinal adipokines and gut hormones induced by Roux-en-Y gastric bypass (RYGB) are considerably different than sleeve gastrectomy (SG), little is known about the consequences on bone health resulted by these two procedures. Objective: to compare the prevalence of secondary hyperparathyroidism (SHPT), bone mineral density (BMD), bone turnover markers and serum leptin in obese patients undergoing RYGB and SG, according to the time of surgery and percent weight loss. Methods: we studied 117 patients (91% female, 51% RYGB, mean age 41.8 ± 6.7 years, mean time of surgery 4.3 ± 3.4 years) who were divided into two groups according to the surgical procedure adopted (SG vs. RYGB). They were evaluated at different times after surgery (1–2 years, > 2 and <5 years and ≥5 years) and according to the percentage of weight loss (10–20%, >20% and <40%, ≥40%). Anthropometric measurements, body composition and BMD, bone parameters (PTH, corrected serum calcium, 25OHD, alkaline phosphatase -AP, C-telopeptide - CTX), and biochemical tests were compared. Results: The prevalence of SHPT (PTH ≥ 65pg/ml) was 26%, higher in the RYGB vs. SG (35% vs. 17%, respectively, p = 0.039), despite no significant differences in serum 25OHD (28.5 ± 7.3 vs. 27.6 ± 7.7 ng/ml, p=0.519) and corrected serum calcium (9.8 ± 0.6 vs. 9.8 ± 0.5 mg/dl, p = 0.466) between the groups. Mean serum PTH, CTX and AP was higher in the RYGB vs. SG (61.3 ± 29.5 vs 49.5 ± 32.3 pg/mL, p = 0.001; 0.596 ± 0.24 vs. 0.463 ± 0.23 ng/mL; 123.9 ± 60.8 vs. 100.7 ± 62.0 U/L, respectively). There were 13.5% decreases in femoral neck BMD in all patients, over the study period. After 5 years of surgery, the RYGB group showed greater bone loss in total body BMD (1.016 vs. 1.151g/cm2, -8.1%, p = 0.003) and total femur BMD (1.164 vs. 1.267g/cm2, - 11.7%, p = 0.007). Mean serum leptin was lower in the RYGB group, when compared to SG (7.6 ± 5.8ng/mL vs. 14.0 ± 9.9, p = 0.001), with no correlation with BMD in any site. There were no significant differences between the RYGB and SG regarding the other metabolic parameters. Conclusion: We found a more deleterious effect of RYGB on bone health up to 5 years postoperatively in comparison with SG.