To evaluate calcium (Ca) metabolism and bone mineral density (BMD) in children with rheumatic disease (RD) at diagnosis and one year later, and effects of different therapies.
We used dual tracer isotope studies and dual energy x-ray absorptiometry (DEXA) to measure Ca metabolism and BMD in 13 children with RD at diagnosis and one year later. Seven subjects were treated with steroids (RD-ST), 6 with antiinflammatory agents (RD-NS), excluding steroids.
Ca balance data for RD subjects were not significantly different from data reported previously for healthy sex and age matched controls. True Ca absorption (Va) was slightly but not significantly greater at study entry in RD-NS subjects (313+/-67 vs 239+/-112 mg/day in RD-ST subjects; p = 0.13). Calculated Ca balance retention (Vbal) was higher at entry in RD-NS (200+/-51 vs RD-ST 60+/-125 mg/day; p = 0.08). One year later, Vbal remained higher in RD-NS (202+/-77 mg/day vs RD-ST 101+/-157 mg/day; p = 0.02). BMD was similar in both groups at entry (RD-NS 0.81+/-0.06 g/cm2 vs RD-ST 0.89+/-0.1 g/cm2; p = 0.07). One year later, BMD was 0.86+/-0.6 g/cm2 in RD-NS versus 0.89+/-0.08 g/cm2 in RD-ST; p = 0.07. Ca kinetic and DEXA studies did not reveal significant alteration of Ca kinetics or significantly lower BMD in steroid treated subjects versus non-steroid treated subjects. However, slightly lower Va and Vbal indicated a possible risk of bone demineralization in steroid treated subjects.
Children with RD who are treated with steroids may be at greater risk of bone demineralization at diagnosis that persists through the first year. However, bone loss may take years to manifest when measured by quantitative methods such as DEXA.