 All participants enrolled in this trial will be vitamin D3 deficient. Participants will take an antibiotic tetracycline 4 times a day to mark the starting point from which bone changes will be assessed. After 3 days of tetracycline, a 12 week course of vitamin D3 or placebo will be initiated. Six of 7 participants will receive the study drug active vitamin D3, while 1 in 7 will receive a placebo sugar pill. Ten weeks later, another 3-day course of tetracycline will be given. At the end of 12 weeks, a bone biopsy will be done. A small piece of bone about the size of a pencil eraser will be removed from the hip iliac crest. The bone will be analyzed to determine the effect of vitamin D3 on primary hyperparathyroidism. 