BACKGROUND: Monitoring treatments of osteoporosis is required to identify patients not responding to the treatment in a way that reflects mechanism of action of the antiresorption drug on bone. Neither bone mineral measurement nor the available biochemical markers of bone remodeling can be used to monitor efficacy of treatment with nasal spray salmon calcitonin (sCT) since the changes in individual patients are modest and do not exceed the least significant change. METHOD: The novel calcitonin load test (CLT) was developed to assess the biological response to sCT in postmenopausal osteoporotic women. The CLT is based on the time course and an extent of suppression of serum C-terminal telopeptide of types I collagen (CTX) after the intranasal and subcutaneous administration of sCT. The CLT was conducted in 30 untreated postmenopausal osteoporotic women (control group, mean age, 67.7+/-8.4 years), and in 120 postmenopausal osteoporotic women (mean age, 68.5+/-8.1 years) treated with 200 IU of sCT (Miacalcic Nasal, Novartis, Switzerland), for up to 8.4 years (mean, 3.5+/-2.1 years). RESULTS: After 90 min from the intranasal administration of 400 IU of sCT, a decrease (p<0.01) in serum CTX by 58+/-11% was found in the control group, and by 60+/-11% in 74% of the treated patients. In the remaining treated patients, the decrease in CTX did not exceed the least significant change. The number of patients not responding to the CLT increased with duration of the treatment up to 34% in patients treated for over 4 years. Of the non-responders to the nasal spray sCT, 63% failed to respond to the subcutaneous administration of 10 IU of sCT. In the treated group, a significant negative correlation has been found between the percentual changes in CTX from its baseline levels detected during the CLT, and a rate of changes in the femoral neck BMD (p<0.01). CONCLUSION: The CLT can be used as a tool to identify patients that respond to administration of CT, and will profit from a continued treatment with sCT.

Department of Internal Medicine 3 Faculty of Medicine 1 Charles University U nemocnice 1 CZ 128 00 Prague Czech Republic

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