Hypovitaminosis D and hyperparathyroidism: a five-year postoperative follow-up of 30,458 gastric bypass and sleeve gastrectomy patients

Background Bariatric procedures are associated with nutrient deficiencies. Studies show an association between gastric bypass (RYGB) and hypovitaminosis D as well as hyperparathyroidism, yet few compare RYGB to sleeve gastrectomy (SG), and large long-term analyses are scarce. Objective Evaluate trends of vitamin D and PTH levels in RYGB and SG Setting National quality register Method The Scandinavian Obesity Surgery Registry records all bariatric surgery in Sweden. Data from 2008 to 2021 on primary RYGB or SG with reported 25-OH-D and/or parathyroid (PTH) levels was included. Individuals with an eGFR <60 ml/min/1.73m2 were excluded, leaving a study population of 25,385 RYGB and 5073 SG patients. Results A decrease in 25-OH-D, mirrored by an increase in PTH was observed after the first year for both procedures, however more pronounced in RYGB. At five years, 25-OH-D levels were still higher than at baseline. Regular supplementation resulted in better 25-OH-D and PTH levels. Linear regression found that procedure type (RYGB vs SG), 25-OH-D levels and time since surgery, were significant factors in predicting PTH levels. The risk of pathological PTH levels (>7 pmol/L) at two and five years postoperatively was roughly three times higher in RYGB (OR 3.41 and 2.84, respectively). Conclusions Previous studies alongside these results suggest that RYGB, more so than SG, may cause hypovitaminosis D, and thereby hyperparathyroidism which could lead to osteopenia. The threshold for 25-OH-D should be above 75 nmol/L, and despite higher levels, current vitamin D supplementation may not be sufficient. Follow up should include screening for hyperparathyroidism and hypovitaminosis D.