Bone Resorption Rate After Bisphosphonate Treatment

Marc C. Hochberg, MD

Disclosures

February 20, 2003

Question

Postmenopausal use of bisphosphonates clearly lowers the bone resorption rate. How does this lower rate compare with the resorption rate of premenopausal women?

Donald R. White, PhD

Response From Expert

Marc C. Hochberg, MD, MPH
Professor of Medicine and Epidemiology and Preventive Medicine, Department of Medicine; Head, Division of Rheumatology and Clinical Immunology, University of Maryland School of Medicine , Baltimore, Maryland

 

In postmenopausal women who are not on hormone therapy, the average rate of bone turnover, as measured by urine and/or serum markers of bone resorption, is elevated above the normal premenopausal level. The normal level is usually described as the mean value plus 2 standard deviations. When such women are treated with bisphosphonates, or other antiresorptive agents, the average rate of bone turnover falls into the normal range for premenopausal women. Hence, in clinical practice, if we use biochemical markers of bone turnover to manage our patients, we would expect that by 3 months after starting a nitrogen-containing bisphosphonate, the level of bone resorption marker would be within the normal premenopausal range.

The normal values of bone turnover markers differ between the different markers and the different tests used to measure them. Clinicians should check with their reference laboratory regarding these tests. The most common commercially available tests are (1) urine N-telopeptide of type I collagen (NTX), (2) urine C-telopeptide of type I collagen (CTX), (3) serum bone-specific alkaline phosphatase (BSAP), and (4) serum CTX.

The studies by Schnitzer and colleagues[1] and Brown and colleagues[2] both show that once-weekly therapy with a bisphosphonate reduces bone turnover markers to the normal premenopausal range just as effectively as does daily therapy. You'd have to go back to the phase 2/3 studies to show such a reduction compared with a smaller effect for the placebo group (that also receives calcium supplementation with or without vitamin D, depending on the study).

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