Combination Risedronate - Parathyroid Hormone Trial in Male Osteoporosis

The purpose of this study is to develop new treatment options for osteoporosis in men. The Investigators will study two medications and three treatment regimens. First, risedronate (FDA approved) will be studied as monotherapy. Second, the investigators will study injectable parathyroid hormone (PTH 134, teriparatide; FDA approved), as a therapy for male osteoporosis. PTH, a naturally occurring hormone produced by the parathyroid glands, is one of the most important regulators of bone metabolism. The drug being studied in this protocol, teriparatide, is the first aminoterminal 34 amino acids of the native 84amino acid peptide. Teriparatide contains all of the classical biological activities of native PTH. In studies of postmenopausal women, in a small study of 23 men with osteoporosis and a larger study of 437 men treatment with teriparatide led to significant increases in bone density. Although teriparatide and actonel are now approved for osteoporosis in men additional studies of these medications are needed in order to establish how best to use these drugs. This study is focused on an entirely new treatment approach, namely the combination of two medications for the treatment of osteoporosis risedronate with teriparatide to evaluate whether combination therapy is superior to therapy with either medication alone. This study is also designed to assess the extent to which risedronate maintains increases in bone density after a course of mono or combination therapy.