High Incidence of Secondary Hyperparathyroidism in Bariatric Patients: Comparing Different Procedures

Abstract

Background: Bariatric surgery is an effective therapy for morbid obesity but may reduce calcium absorption and significantly decrease the bone mineral density. This study examined the prevalence of secondary hyperparathyroidism (SHPT) in obese subjects during follow-up after different bariatric surgeries. We investigated predictors of SHPT.

Methods: We enrolled 1470 obese subjects undergoing bariatric/metabolic surgery with at least 1-year follow-up, including 322 patients undergoing Roux-en-Y gastric bypass (RYGB), 695 undergoing single anastomosis (mini-) gastric bypass (SAGB), 93 undergoing laparoscopic adjustable gastric banding (LAGB), and 360 undergoing sleeve gastrectomy (SG). Five years of data were available for 215 patients. Patients were instructed to supplement their diet according to the guideline. Calcium, parathyroid hormone (PTH), and vitamin D levels were measured before surgery and at 1 and 5 years after surgery. SHPT was defined as PTH > 69 pg/mL.

Results: The overall prevalence of SHPT was high, 21.0% before surgery and was not different between patients with different bariatric procedures. Pre-operative PTH correlated with age, BMI, and vitamin D levels. Multi-variate analysis confirmed that vitamin D level was the only independent predictor of SHPT before surgery. The prevalence of SHPT increased to 35.4% at 1 year after surgery and 63.3% at 5 years after surgery. SAGB had the highest prevalence of SHPT (50.6%) followed by RYGB (33.2%), LAGB (25.8%), and SG (17.8%) at 1 year after surgery. At 5 years after surgery, SAGB still had the highest prevalence of SHPT (73.6%), followed by RYGB (56.6%), LAGB (38.5%), and SG (41.7%). Serum PTH at 1 year after surgery correlated with decreased BMI and weight loss. Multi-variate analysis confirmed that age, sex, calcium level, and bypass procedure were independent predictor of SHPT after surgery.

Conclusions: The prevalence of SHPT is high in morbidly obese patients before bariatric surgery which is related to vitamin D deficiency. The prevalence of SHPT increased continually along with the time after bariatric surgery, especially in patients receiving SAGB, followed by RYGB. The supplementation of vitamin D and calcium have to be higher in bypass procedure, especially in malabsorptive procedure.

Keywords: Bariatric surgery; Hyperparathyroidism; Morbid obesity.