Hypovitaminosis D and hyperparathyroidism: a 5-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 (Roux-en-Y 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 parathyroid hormone (PTH) levels in RYGB and SG.

Setting

National quality register.

Method

The Scandinavian Obesity Surgery Registry records all bariatric surgeries in Sweden. Data from 2008 to 2021 on primary RYGB or SG with reported 25-hydroxy vitamin D (25-OH-D) and/or PTH levels were included. Individuals with an estimated glomerular filtration rate of <60 mL/min/1.73 m² 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, but more pronounced in RYGB. At 5 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 versus SG), 25-OH-D levels, and time since surgery were significant factors in predicting PTH levels. The risk of pathologic PTH levels (>7 pmol/L) at 2 and 5 years postoperatively was roughly three times higher in RYGB (odds ratios = 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 >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.