This is a randomized placebo controlled, double blind study. Patients who meet eligibility criteria and decide to participate in the study will be randomly assigned to receive either drug treatment or a placebo. Neither the patients nor the participating investigators will know who is receiving the drugs and who is receiving the placebo. Participation involves 15 outpatient clinic visits over a 68 week period. Patients take study medication at varying doses (the maximum dose is 20 mg daily), along with calcium and vitamin supplements.