 1. To evaluate the effect of vitamin D3 therapy on CaAb in postmenopausal women less than or equal to 75 years old with VDI. Sub-aims include the investigation of subject variables influencing CaAb and 25OHD levels at baseline and one month, the accuracy of oral isotope plasma levels for CaAb measurement and the ability of a questionnaire to identify patients with low vitamin D status. 