Biochemical markers of bone metabolism in relation to adrenocortical and growth suppression during the initiation phase of inhaled steroid therapy

Abstract

Growth suppression is usually most evident during the first year of inhaled steroid therapy. Steroid-induced changes in bone metabolism may contribute to this growth suppression. The aim of the present study was to evaluate the changes in biochemical markers of bone metabolism in relation to adrenal and growth suppression during the initiation phase of inhaled steroid therapy. Seventy-five school-aged children with new asthma were enrolled into budesonide (BUD, n = 30), fluticasone propionate (FP, n = 30) or cromone (CROM, n = 15) treatment groups. BUD dose was 800 microg/d during the first two months and 400 microg/d thereafter. The respective FP doses were 500 and 200 microg/d. Biochemical markers of bone metabolism were measured before treatment and after 2 and 4 mo of therapy. In the control (CROM) group, the mean concentrations of serum osteocalcin (OC), carboxyterminal propeptide of type I procollagen (PICP) (formation markers) and type I collagen carboxyterminal telopeptide (ICTP) (degradation marker) tended to increase. In the BUD group, OC and PICP decreased during the 4 mo by a mean of 23% (p < 0.001) and 15% (p < 0.05), respectively, while ICTP did not change significantly. In the FP group, OC and ICTP decreased during the first 2 mo by a mean of 19% (p < 0.01) and 21% (p < 0.01), respectively, returning to the pretreatment level at 4 mo, while PICP tended to increase during the 4 mo (14%, p = 0.12). In the steroid treated children whose height SD score decreased during the first 12 mo of therapy, both OC and PICP decreased during the first 4 mo by a mean of 20% (p < 0.01) and 21% (p < 0.001), respectively. In those children who had no growth suppression, the changes were not significant: -4% in OC and +13% in PICP. Furthermore, in children who developed evidence of adrenocortical suppression (on the basis of a low-dose ACTH test), OC decreased more (23%, p < 0.01) than in those with normal adrenocortical function (10%, p = 0.06). In conclusion, both inhaled BUD and FP caused dose-dependent effects on biochemical markers of bone metabolism. The children who developed growth or adrenocortical suppression were likely to have changes also in bone metabolism.