Intestinal hyperabsorption of calcium (Ca) is frequently observed in sarcoidosis and is characteristic of absorptive hypercalciuria (AH). The potential pathogenetic role of 1α,25-dihydroxyvitamin D [1,25(OH)2D] in these two conditions was sought by a careful assessment of the circulating concentration of this vitamin D metabolite and various measures of Ca metabolism before and after prednisolone therapy. In eight patients with sarcoidosis, prednisolone treatment (50 mg/day for 8 days) produced a significant fall in serum 1,25(OH)2D [4.8 ± 1.9 to 3.3 ± 1.0 (SD) ng/dl; P < 0.025], concomitant with a significant decrease in the fractional intestinal Ca absorption (a) from 0.58 ± 0.14 to 0.46 ± 0.13 (±SD; P < 0.005). Urinary Ca and serum parathyroid hormone did not change significantly. However, in six patients with AH, prednisolone therapy resulted in a nonsignificant rise in serum 1,25(OH)2D from 3.6 ± 0.7 to 4.4 ± 1.0 ng/ dl and no significant fall in a (from 0.73 ± 0.08 to 0.70 ± 0.10). Urinary Ca was significantly increased in AH patients from 230 ± 35 to 343 ± 74 (SD) mg/day (P < 0.005), while serum parathyroid hormone rose slightly. Serum 1,25(OH)2D and ex were significantly correlated (r = 0.543; P < 0.05) for patients with sarcoidosis but not in AH patients. These results suggest that the hyperabsorption of calcium in sarcoidosis is dependent on the serum concentration of 1,25(OH)2D, while in AH it may result from additional vitamin D-independent processes.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical