Secondary hyperparathyroidism following biliopancreatic diversion.

OBJECTIVE: To investigate the cause of osteomalacia following biliopancreatic diversion(BPD) surgery for obesity.
DESIGN: A retrospective, case-comparison study.
SETTING: A tertiary care center. PATIENTS: A case group of 12 subjects (including 9 women; mean age +/- SEM, 48.5 +/- 3.0 years; mean preoperative body mass index +/- SEM, 43.7 +/- 2.3 kg/m2, and mean weight loss +/- SEM, 75 +/- 14 kg) who have undergone BPD (referred to as BPD group hereafter) and a comparison group of 10 subjects (including 9 women; mean age +/- SEM, 49.6 +/- 3.3 years; mean preoperative body mass index +/- SEM, 44.0 +/- 2.5 kg/m2; and mean weight loss +/- SEM, 55 +/- 15 kg) following vertical banded gastroplasty (VBG) (referred to as VBG group hereafter). MAIN OUTCOME MEASURES: Serum and urine markers for bone metabolism.
RESULTS: Compared with the VBG group, the BPD group had significantly lower concentrations of the following components: serum calcium (2.14 +/- 0.05 mmol/L vs 2.37 +/- 0.05 mmol/L [8.6 +/- 0.2 mg/dL vs 9.5 +/- 0.2 mg/dL]), serum 25-hydroxyvitamin D (24 +/- 6 nmol/L vs 64 +/- 6 nmol/L), urine calcium excretion (1.7 +/- 0.7 mmol/d vs 4.5 +/- 0.7 mmol/d [68 +/- 28 mg/d vs 180 +/- 28 mg/d]), and serum carotene (0.40 +/- 0.15 mmol/L vs 1.29 +/- 0.16 mmol/L). The BPD group had significantly higher concentrations of the following components: serum parathyroid hormone (13.6 +/- 2.1 pmol/L vs 5.2 +/- 2.3 pmol/L), serum alkaline phosphatase (139 +/- 8 U/L vs 86 +/- 9 U/L), and urinary hydroxyproline/creatine (52 +/- 5 mumol/mmol vs 19 +/- 5 mumol/mmol).
CONCLUSION: These data suggest that following BPD, secondary hyperparathyroidism attributed to hypocalcemia results from malabsorption of vitamin D. However, we cannot exclude the possibility of concurrent calcium malabsorption with vitamin D malabsorption.