This study is a prospective, observational, single-center study. Ethical approval was obtained from the Institutional Review Board.~This study will be completed with 40 premenopausal healthy volunteer women. An intravenous cannula will be inserted into the antecubital vein. Blood samples will be obtained at the beginning (between 2-5th day), mid (between 11-13th day) and end (between 21-23th day) of menstrual cycle.~Serum will be collected and will be centrifuged for 15 minutes at 1000Xg within 30 minutes of collection. Aliquots of plasma will be added to Ependorf tubes and stored at -20°C.~Plasma sclerostin levels will be measured using a Human Sclerostin ELISA kit (Cusabio, Catalog No: CSB-E13146h, Newark, DE, USA). All assays will be performed according to the manufacturer's instructions. The minimum detectable concentration of human sclerostin is typically <0.012 ng/ml. Intra-assay precision is less than 8%.~Estradiol and progesterone levels will be analyzed in serum samples using an electrochemiluminescence immunoassay (Elecsys PTH, Elecsys-estradiol II; Roche Diagnostics, Mannheim, Germany) and the Cobas 601 analyzing system (Roche Diagnostics).~Free testosteron levels will be analyzed in serum samples using an RIA (radio immun assay) (DSL 4900 Testosterone, Free, Active® RIA Assay kit, Beckman Coulter) and the DSL 4900 Berthold Technologies Multi Crystal LB 2111 model gama counter.
The aim of this study is to determine whether plasma sclerostin levels is affected by sex hormones during menstrual cycle. Blood samples will be obtained at the beginning (between 2-5th day), mid (between 11-13th day) and end (between 21-23th day) of menstrual cycle. Serum sclerostin, estradiol, progesterone and testosteron levels will be measured blindly by only one investigator