Background: Precise calcium (Ca) and vitamin D intestinal absorption after gastric bypass (GB) remains unknown. We evaluated the effect of receiving or not Ca and vitamin D supplementation on Ca, PTH, and vitamin D axis in patients undergoing GB.
Methods: Two hundred twenty-two patients were evaluated prior to GB and at 1 year. Baseline characteristics were registered, and bone metabolism markers were determined before surgery and at 12 months. After surgery, oral calcium carbonate (1,200 mg/daily) and vitamin D3 (800 IU) were prescribed with PTH >70 pg/ml.
Results: In the whole group, before surgery and at 1 year, 36 and 30% had hyperparathyroidism (HPT), respectively. Baseline vitamin D deficiency (<50 nmol/L) was observed in 52% with insufficiency (50-75 nmol/L) in 28%. Linear regression analysis showed a significant positive relationship between PTH and excess body weight (EBW) (r 0.190) with a significant negative relationship between PTH and 25 (OH) D (r-0.243). Only EBW was independently associated with HPT on multivariate logistic regression. PTH and 25 (OH) D significantly improved at 1 year with Ca supplementation, but HPT continued in 35 and in 71%, 25 (OH) D was <75 nmol/L. 25 (OH) D only increased 11.5 nmol/L with supplementation. Without Ca supplementation, both PTH and 25 (OH) D increased. HPT developed in 15% with 25 (OH) D < 75 nmol/L in 66%.
Conclusions: Ca and vitamin D supplementation after GB should be universal and individualized to overcome mal-absorption and improve previous 25 (OH) D deficiency.