Effects of rheumatic disease and corticosteroid treatment on calcium metabolism and bone density in children assessed one year after diagnosis, usingstable isotopes and dual energy X-ray absorptiometry

Objective. To evaluate calcium (Ca) metabolism and bone mineral density (BM D) in children with rheumatic disease (RD) at diagnosis and one year later, and effects of different therapies. Methods. We used dual tracer isotope studies and dual energy x-ray absorpti ometry (DEXA) to measure Ca metabolism and BMD in 13 children with RD at di agnosis and one year later. Seven subjects were treated with steroids (RD-S T), 6 with antiinflammatory agents (RD-NS), excluding steroids. Results. Ca balance data for RD subjects were not significantly different f rom data reported previous ly for healthy sex and age matched controls. Tru e Ca absorption (Va) was slightly but not significantly greater at study en try 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/cm (2) vs RD-ST 0.89 +/- 0.1 g/cm(2); p = 0.07). One year later, BMD was 0.86 +/- 0.6 g/cm(2) 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 kineti cs or significantly lower BMD in steroid treated subjects versus non-steroi d treated subjects. However, slightly lower Va and Vbal indicated a possibl e risk of bone demineralization in steroid treated subjects. Conclusion. Children with RD who are treated with steroids may be at greate r risk of bone demineralization at diagnosis that persists through the firs t year. However, bone loss may take years to manifest when measured by quan titative methods such as DEXA.