Endocrine Abstracts

Background: Osteoporosis has been an excruciating disease for many years now. Although various treatments are available, there is an unmet need for disease prognosis, early disease diagnosis and prediction of treatment efficacy. New biomarkers are crucial for the diagnosis or prognosis of a disease as well as for monitoring treatment efficacy and improve decision making. Cathepsin K is a cysteine protease that cleaves collagen type I, the major type of collagen found in bone, so it is useful to measure to assess the function and number of osteoclasts. The aim of the current study was to evaluate the fluctuation of cathepsin K, phosphorus, 25 HO vitamin D, alkaline phosphatase and PTH before and after 6 and 12 months of treatment with alendronate.

Methods: We conducted a longitudinal study with a cohort of 28 female patients with osteoporosis and 15 healthy controls. All subjects were menopaused, non-diabetic, non-obese, without secondary osteoporosis. All patients were treated with alendronate and calcium and vitamin D supplements. Serum samples were collected longitudinally before treatment, at 6 and 12 months post treatment initiation and the levels of cathepsin K, phosphorus, 25 HO vitamin D, alkaline phosphatase and PTH were measured\. Basal serum cathepsin K levels were also compared to premenopausal women without osteoporosis (n=15).

Results: We observed that serum cathepsin K levels were higher in premenopausal women with osteoporosis (9746.07+/−1824 RFU/ml) compared with healthy premenopausal women (7747.33+/−762.67 RFU/ml; P<0.01). Also, serum cathepsin K decreases gradually after alendronate treatment (5.09% at 6 months, and 7,17% at 12 months, P<0.05). We also found a positive association of cathepsin K and phosphorus and alkaline phosphatase and a negative association with 25 HO vitamin D.

Conclusion: We conclude that serum cathepsin K may serve as an additional biomarker for bone metabolism and alendronate treatment monitoring besides phosphorus and alkaline phosphatase. The role of Cathepsin K as a risk biomarker marker in premenopausal women without osteoporosis is also discussed.