THE EFFECT OF INTRANASAL SALMON-CALCITONIN ON POSTMENOPAUSAL BONE TURNOVER AS ASSESSED BY BIOCHEMICAL MARKERS - EVIDENCE OF MAXIMAL EFFECT AFTER 8 WEEKS OF CONTINUOUS TREATMENT

Although treatment with intranasal salmon calcitonin (sCT) has been sh own to effectively inhibit postmenopausal bone loss, there is still co ntroversy over both timing and the duration of its application. In an open prospective study, we therefore assessed the effect of shortterm intranasal sCT on postmenopausal bone turnover, employing biochemical markers of bone metabolism. Ten early postmenopausal, previously untre ated women (1-5 years after menopause) with biochemical evidence of in creased bone resorption and a low bone mineral density at baseline wer e treated with intranasal sCT (100 IU B.I.D.) for a period of 3 months . Oral calcium (500 mg/day) was administered simultaneously, and durin g a further 3 month followup interval. Treatment with sCT resulted in a pronounced suppression of bone resorption markers with a maximum eff ect reached after 8 weeks of therapy: as compared to the respective ba seline values, mean levels decreased by -26.2% +/- 3.4% (P < 0.001) fo r pyridinoline, -32.7% +/- 3.5% (P < 0.001) for deoxypyridinoline, -32 .7% +/- 3.3% (P < 0.001) for hydroxyproline, and -24.1% +/- 8.2% (P < 0.001) for the amino-terminal telopeptide. In contrast, changes in bon e formation markers of osteocalcin (-14.4% +/- 4.8%, P < 0.05) and C-t erminal procollagen type I propetide (-7.9% +/- 3.9%, ns) were much le ss pronounced. Unexpectedly, after week 8 of the study all resorption markers showed a plateau and a trend to increase, although intranasal sCT was continued for a total of 12 weeks. This effect could not be at tributed to the formation of anti-sCT antibodies. After cessation of t reatment, both bone formation and resorption markers rapidly returned to baseline levels. Bone mineral density of both spine and hip showed no significant change during the observation period. Our results demon strate that in postmenopausal women with a high bone turnover? intrana sal treatment with 200 IU of sCT effectively reduces bone turnover and maintains bone mass, the maximum effect being reached after 8 weeks o f treatment.