Bone density and 25-OH-vitamin D in systemic lupus erythematosus

Objective To clarify the influence of Vitamin D metabolism on bone mineral density (BMD) or bone metabolism in patients with systemic lupus erythematosus (SLE). Methods 57 consecutive patients in our department (mean age 33.9 years, 44 female, 13 male) were studied. BMD was measured with dual-Xray absorptiometry at the lumbar spine and femoral neck. Biochemical investigation of bone metabolism included measurement of vitamin D metabolites, intact parathyroid hormone (PTH), serum osteocalcin and urinary pyridinoline-crosslink excretion. Results 25 patients had 25-OH cholecalciferol serum values below the normal range after adjustment for seasonal changes; 9 patients were severely vitamin D depleted with 25-OH vitamin D serum values below 5 ng/ml. Low 25-OH-vitamin D was significantly associated with high disease activity. Mean 1.25 (OH)(2)-vitamin D, PTH, osteocalcin and crosslink excretion were in the normal range. Thirty-six patients had normal BMD; 5 patients had osteoporosis according to WHO diagnosis criteria. No correlation of biochemical parameters of bone metabolism with BMD was found. Conclusion Severe vitamin D depletion was common in this group of patients with SLE even after adjustment for seasonal variations, especially in patients with high disease activity. Therefore, D-hypovitaminosis should be included in the differential diagnosis in patients with SLE presenting with low bone mass.