The objective of this study is to characterise the dose-response curve for ronacaleret with respect to safety and efficacy based on changes in peripheral CD34+ cell counts. Results obtained from this study will inform us: of optimized doses, schedules, and durations of treatment for future studies. Additional cohorts may be added to further explore the dose schedule and duration if required. The exact number of cohorts studied will depend on the results obtain from the prior groups and the desire to explore a variety of doses and schedules. The aims of the present study (CR9115166) include an assessment of the pharmacodynamic effects (mobilization of CD34+ cells), safety, tolerability, and pharmacokinetics of ronacaleret in healthy human volunteers.