Vitamin D-mediated calcium absorption in patients with clinically stable Crohn's disease: a pilot study

Abstract

Vitamin D is the critical hormone for intestinal absorption of calcium. Optimal calcium absorption is important for proper mineralization of bone in the prevention of osteoporosis and osteoporotic fractures, among other important functions. Diseases associated with gut inflammation, such as Crohn's disease (CD), may impair calcium absorption. This pilot study evaluated vitamin D- dependent calcium absorption in subjects with CD. Male subjects with CD (n=4) and healthy age-matched controls (n=5) were studied. All subjects had fractional calcium absorption (FCA; by the dual calcium isotope method), serum 25-hydroxyvitamin D, serum calcium and 24 h urinary calcium excretion measurements at baseline. The FCA in response to vitamin D therapy was re-assessed following administration of oral calcitriol 0.25 mcg twice daily for 1 wk, followed by oral calcitriol 0.50 mcg twice daily for 1 wk. Serum calcium and 24 h urinary calcium determinations were re-assessed after each increasing dose of calcitriol as safety measures. There was no significant difference in calcium FCA at baseline or after increasing doses of calcitriol between the CD and controls. FCA in the control and CD group was approximately 35% at baseline, which increased to 60% after calcitriol therapy. No subject developed hypercalcemia or hypercalciuria. Our results suggest that CD patients have a normal response to vitamin D in enhancing the efficacy of calcium absorption. This suggests that stable CD patients can follow calcium and vitamin D guidelines of non-CD adults. Other factors independent of vitamin D status may impair intestinal calcium absorption in CD, including the degree and location of inflammation, presence of surgical resection and/or use of glucocorticoids.

Trial registration: ClinicalTrials.gov NCT00427804.

Conflict of interest statement

The authors have declared no conflict of interest.

Figures

Figure 1

Experimental methodology.

Figure 2

Twenty-four-hour urine calcium levels in CD subjects and controls. Male subjects with CD (black diamonds) and healthy matched controls (white boxes) underwent determination for 24 h urine calcium excretion at baseline and in response to calcitriol at two doses (0.25 mcg twice daily and 0.50 mcg twice daily). There were no significant differences in the 24 h excretion of calcium comparing the CD and control groups.

Figure 3

FCA in CD subjects and controls. Male subjects with CD (black diamonds) and healthy matched controls (white boxes) underwent determination of FCA using dual stable calcium isotopes at baseline and in response to calcitriol at two doses (0.25 mcg twice daily and 0.50 mcg twice daily). Both groups had similar FCA at baseline. There were no significant differences in FCA in response to both doses of calcitriol comparing the CD and control groups.