We are enrolling postmenopausal women that are on chronic corticosteroid therapy (prednisone etc.) and have bone loss (osteopenia by DXA) to be a part of this four-year-long study. The patients will receive two-year therapy with either PTH (1-34) or placebo, and for the second part of the study subjects receive either estrogen and placebo or alendronate and placebo. We will measure bone gain by standard bone densitometry, special x-rays of the spine and hip, and serum and urine bone markers.