Urinary osteocalcin and other markers of bone metabolism: the effect of risedronate therapy.
OBJECTIVE
Serum osteocalcin (S-OC) is widely used as an index of bone formation. However, there is evidence that some urinary fragments of OC reflect resorption and might be useful in monitoring antiresorptive therapy. Here, we report 6-month changes in urinary midfragments of osteocalcin (U-MidOC) and other bone turnover markers in response to risedronate treatment.


METHODS
The study group comprised 19 patients with postmenopausal osteoporosis, aged 49-66 years, and receiving risedronate therapy. Fifty-four premenopausal women served as controls. Osteoporosis was diagnosed by lumbal bone mineral density (BMD). Urinary osteocalcin was measured by the U-MidOC assay for midfragments. Bone formation was assessed by S-PINP and S-OC, and resorption by S-CTx-I.


RESULTS
At baseline, U-MidOC was significantly correlated only with S-OC. After the 1st month of therapy, a similar decrease was observed in the values of U-MidOC and S-CTx-I, but in formation markers S-P1NP and S-OC only after three months. The rapid decrease in U-MidOC, analogous to S-CTX-I, and the different kinetics for urinary and serum OC suggest that urinary OC midfragments are more associated with resorption than S-OC. An association was also observed between the 1-month change in U-MidOC and 12-month gain in lumbar BMD. The response in U-MidOC after only the 1st month of therapy makes it a potential marker for monitoring the effect of risedronate, presumably reflecting different aspects of bone resorption than S-CTx-I does.
Kumm
Jaanika
J
Clinic of Internal Medicine, University of Tartu, Tartu, Estonia. Jaanika.Kumm@kliinikum.ee
Ivaska
Kaisa K
KK
Rohtla
Kadri
K
Vaananen
Kalervo
K
Tamm
Agu
A
D000368:Aged; D015415:Biomarkers / Q000652:urine; D015519:Bone Density / Q000187:drug effects; D012968:Etidronic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008875:Middle Aged; D015675:Osteocalcin / Q000652:urine*; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy* / Q000652:urine*; D000068296:Risedronic Acid; D013997:Time Factors
D015415:Biomarkers; D015675:Osteocalcin; D000068296:Risedronic Acid; D012968:Etidronic Acid