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Serum cathepsin K concentrations reflect osteoclastic activity in women with postmenopausal osteoporosis and patients with Paget's disease


INTRODUCTION: Cathepsin K, a cysteine protease, plays an essential role in osteoclast-mediated collagen degradation. Recently, an immunoassay to quantify cathepsin K in serum has been developed. We assessed the usefulness of serum cathepsin K as a marker of bone turnover in cross-sectional and longitudinal studies of patients with metabolic bone disease. METHODS: The study cohort consisted of 40 healthy subjects, 21 women with postmenopausal osteoporosis [66.1 +/- 7.9 yrs] and 10 patients with Paget's disease of bone [67.1 +/- 11.6 yrs]. All patients were started on oral or intravenous bisphosphonate treatment and were followed prospectively over 6 months. Circulating cathepsin K levels were determined by a specific sandwich enzyme immunoassay (Biomedica, Vienna, Austria). In addition, serum carboxyterminal cross-linked telopeptide of type I collagen (betaCTX-I) and bone-specific alkaline phosphatase (BALP) were measured for comparison. RESULTS: When compared to healthy subjects, mean serum cathepsin K levels were significantly elevated in women with postmenopausal osteoporosis (3.1 +/- 1.9 vs. 11.3 +/- 13.1 pmol/L, p = 0.01) and in patients with Paget's disease of bone (6.2 +/- 4.4 pmol/L, p = 0.04). In postmenopausal osteoporotic women, both oral and intravenous bisphosphonate treatment resulted in a significant reduction in serum cathepsin K levels (p = 0.03) with most of the effect occurring after one month (mean% change: -33%). In patients with mild Paget's disease, serum cathepsin K levels decreased during bisphosphonate treatment. CONCLUSIONS: Serum concentrations of cathepsin K appear to reflect osteoclastic activity in patients with postmenopausal osteoporosis and Paget's disease of bone and may hold promise as a marker of osteoclast activity.

Type Journal
ISBN 1433-6510 (Print)
Authors Meier, C.;Meinhardt, U.;Greenfield, J. R.;De Winter, J.;Nguyen, T. V.;Dunstan, C. R.;Seibel, M. J. :
Publisher Name Clinical Laboratory
Published Date 2006-01-01
Published Volume 52
Published Issue 1-2
Published Pages 1-10
Status Published in-print
URL link to publisher's version