Alendronate is an aminobisphosphonate, a selective inhibitor of osteoclast-mediated bone resorption. Due to its influence a decline of markers of bone turnover occurs. The latter react much sooner than it is possible to detect significant changes of bone density. In the submitted trial the authors investigated changes of selected markers: total alkaline phosphatase (ALP), osteocalcin (OC), N-terminal telopeptide fragment of collagen type I (NTx) after 3 months´ treatment with alendronate, the influence on bone density after one year´s treatment in 50 postmenopausal women with densitometrically verified osteoporosis. After one-year treatment in the whole group a significant increase of bone density occurred in the area L2-L4 by 4.52 % (SD = 3.9), neck of the femur by 2.24 % (SD = 3.6), trochanter by 2.81 % (SD = 3.0) and total by 1.89 % (SD = 2.7). Total ALP and OC in serum, similarly as NTx in urine declined significantly already after 3 months treatment and the decline persisted also after one year of treatment. With the change of bone density after one year correlated significantly only NTx. A decline of NTx after 3 months by more than 30% as compared with the baseline value was recorded in 81 % patients and this change predicted a significant rise of the bone density in the area of the neck of the femur, on average by 30.Urinary NTx is a promising predictor of the effect of alendronate treatment. Its drop by more than 30 % after 3 months justifies the assumption that bone density increased after one year´s treatment.

        Key words: Alendronate - Bone density - Markers of bone metabolism