Raloxifene is an approved SERM for the prevention and treatment of postmenopausal osteoporosis. Calcitonin is a SERM that reduces spinal fractures (but no other types of fractures.) Calcitonin is also a naturally occurring hormone.
Ask your doctor to help you decide which, if any SERM is appropriate for you.
Bibliography1 Medicinenet.Definition of SERM. Medicinenet. Retrieved: July 31, 2006
2 National Osteoporosis Foundation. Medications To Prevent & Treat Osteoporosis. National Osteoporosis Foundation Retrieved April 29, 2006.
3 Osborne, Zhao, Fuqua, Selective estrogen receptor modulators. Breast Center and Departments of Medicine and Molecular and Cellular Biology, Baylor College of Medicine Retrieved July 31, 2006.

