Secondary Hyperparathyroidism in Patients with Biliopancreatic Diversion After 10 Years of Follow-up, and Relationship with Vitamin D and Serum Calcium

Abstract

Background: Secondary hyperparathyroidism (SHPT) is a matter of concern after biliopancreatic diversion (BPD). The aim of this study was to investigate the relationship between SHPT, 25(OH)D, and calcium after BPD.

Design: A retrospective analysis in obese patients after BPD performed between 1998 and 2016.

Methods: Patients with at least 1 year of follow-up were included. SHPT was considered when PTH > 65 pg/mL in the absence of an elevated corrected calcium. 25(OH)D (ng/mL) status was defined as: deficiency < 20, insufficiency 20-29.9, and sufficiency ≥ 30.

Results: In total, 321 patients were included (76.6% women), with mean age 43.0 (10.5) years. Median follow-up was 6.0 (IQR 3.0-9.0) years. Mean body mass index was 49.8 (7.0) kg/m². SHPT increased to a maximum of 81.9% in the ninth year of follow-up (95% CI: 1.5-9.1). Two years after surgery, 33.9% of patients with 25(OH)D sufficiency had SHPT (p = 0.001). Corrected calcium levels were lower in patients with PTH > 65 pg/mL when compared with PTH < 65 pg/mL; 1 year: 8.96 vs 9.1 mg/dL and 5 years: 8.75 vs 9.12 mg/dL (p < 0.01). After surgery, patients with PTH > 65 pg/mL and 25(OH)D sufficiency had lower corrected calcium levels when compared with subjects with PTH and 25(OH)D in normal range. Two years: 9.0 vs 9.2 mg/dL (p < 0.05) and 4 years: 8.9 vs 9.2 mg/dL (p < 0.01).

Conclusions: Once 25(OH)D is sufficient, the increase in PTH persists associated with a decrease in serum corrected calcium. It is important to ensure a sufficient calcium intake in these patients in order to avoid SHPT and osteomalacia in the future.

Keywords: Bariatric surgery; Biliopancreatic diversion; Hyperparathyroidism; Parathyroid hormone; Serum calcium; Vitamin D.