Bone turnover and inhaled corticosteroids.

Bone turnover and inhaled corticosteroids We wish to take issue with several statements made by Kerstjens et al in their recent paper (July 1994;49:652-6). We believe that their conclusion that there is no clear evidence of a detrimental effect of inhaled corticosteroids on bone metabolism is unsubstantiated by the results of their study. They were able to demonstrate a significant fall in osteocalcin levels after four weeks of inhaled corti-costeroid treatment, which implies a reduction in bone formation. This fall was no longer evident after two years of treatment. A less benign interpretation of these results is that reduced bone formation occurred at the start of treatment,' resulting in a fall in bone density. At a later stage bone metabolism may have returned to its previous equilibrium; any bone loss may not have been rectified by a later increase in bone formation. Unfortunately it is impossible to put the authors' results into a clinical context because they importantly failed to measure bone density. A confounding factor in the interpretation of the effects of inhaled corticosteroids is the effect of courses of systemic corticosteroids. Some patients in study II of their paper must have received systemic corticosteroids yet we are given no information about this. It would be important to know whether the control and treated groups received equivalent doses of systemic corticosteroids over the 2-5 year study period. The authors question the validity of osteo-calcin measurements and suggest that measurement of serum levels of propeptide of type I collagen (PICP) may be a more valid marker of bone formation than osteocalcin (which was measured in our study). Nevertheless there is contrary evidence indicating that PICP may be a less sensitive marker of bone formation than osteocalcin.2 Our study on the effects of inhaled be-clomethasone dipropionate on bone metabolism and density3 is referenced by Kerstjens et al as one of several previous studies on the subject which were short term and uncontrolled. In fact, our study did include a well matched control group of patients with asthma who had not previously received corti-costeroids. Furthermore, the median duration of treatment among the asthmatic subjects in our study who were receiving high dose inhaled corticosteroids was three years. Bone density in asthmatic patients taking high dose inhaled beclo-methasone dipropionate and intermittent sys-temic steroids. AUTHORS' REPLY We believe there are three relevant questions at stake with respect to inhaled corticosteroids and bone turnover. (1) …