 During this research the investigators administer PTHrP to healthy young volunteers in a controlled, continuous intravenous manner. As research subjects complete the week-long study without adverse effects, the dose of PThrP will be increased in later subjects. In the event of a significant adverse effect, immediate action will be taken to reverse it. The investigators want to estimate the effect of a sustainable level of mild hypercalcemia achieved by a week-long intravenous infusion of PTHrP has on vitamin D metabolism, markers of bone turnover and fractional excretion of calcium. 