Inappropriate hypercalcitriolemia in ileum-resected patients with Crohn's disease.

Twelve patients who had undergone ileal resection because of Crohn's disease were studied for measurements of serum 25-hydroxyvitamin D3 (25-OHD3), 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], intact parathyroid hormone (PTH), ionized calcium and phosphate in median 6 years after the intestinal resection. 24 normal subjects matched for age, sex and season served as controls. Despite a reduced level of 25-OHD3 (p less than 0.05) and normal levels of ionized calcium, PTH, phosphate and renal function the median level of 1,25(OH)2D3 was significantly raised (p less than 0.001). Further analysis showed that the inappropriately increased level of 1,25(OH)2D3 was significantly positive related to the concentrations of its substrate (25-OHD3) and PTH. The cause for inappropriate hypercalcitriolemia is uncertain. Contribution from extrarenal 1-hydroxylation of 25-OHD3 as in sarcoidosis is suggested.