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Susan Greenspan

University of Pittsburgh Schools of the Health Sciences

Hormone PTHrP Leads to Significant Increase in Bone Mineral Density According to University of Pittsburgh Study

PITTSBURGH, February 5, 2003 Large doses of a bone anabolic hormone called parathyroid hormone-related protein, PTHrP, increases spine bone mineral density in post-menopausal women by almost five percent in only three months, according to a study at the University of Pittsburgh School of Medicine.

The study is published in the February issue of the Journal of Clinical Endocrinology and Metabolism.

Our study results were remarkable since PTHrP was found to produce significant results in only three months when it would normally take as much as one to three years for this much of an increase to occur using most currently available treatments, said Mara Horwitz, M.D., assistant professor of clinical medicine in the division of endocrinology and metabolism and lead investigator in the study. Even though this was a small study, this research takes us one step further in identifying an anabolic agent that can be effective even in the short term.

The double blind, placebo controlled randomized clinical study enrolled 16 postmenopausal women with osteoporosis between the ages of 50 and 75. All had been on hormone replacement therapy for an average of eight years and still had osteoporosis. Women who had been taking any other type of osteoporosis medication were excluded from the study. Half of the participants received a self-administered injection of PTHrP and the other half received a placebo. The patients were followed for three months.

Despite the large dose of PTHrP as compared to other osteoporosis medications, participants tolerated the treatment without developing hypercalcemia, hypotension, nausea, flushing or other adverse effects.

The rate of bone mineral density increase of 4.7 percent in such a short time period is larger than the rate observed using most of the currently available anti-resorptive osteoporosis medications, said Andrew Stewart, M.D., chief of the division of endocrinology and metabolism at the University of Pittsburgh and senior author of the study. Increases of this magnitude have not been reported using calcitonin or raloxifene even when they are used for as long as three years. They compare very favorably to the recently approved parathyroid hormone (PTH), a very exciting newly FDA-approved bone anabolic agent for osteoporosis.

Even though the study was designed as a pilot, the results were surprisingly more favorable than expected, according to Dr. Stewart. Because of the small number of participants, a larger study will be needed to confirm the results. Also, he added, no data are available on the PTHrPs ability to prevent fractures.

PTHrP is one of several normal hormones that regulate calcium metabolism. It was discovered by several investigators including Dr. Stewart in 1987 and is responsible for hypercalcemia in cancer patients. Since that time, Dr. Stewarts research has led to the purification, sequencing and synthesis of PTHrP.

Based on the results of this study, Dr. Stewart has formed a company, Ostotrophin, L.L.C., to enable large-scale studies of PTHrP for commercialization.

The University of Pittsburgh division of endocrinology and metabolism has a long-standing tradition of excellence in patient care and research in endocrinology and metabolism, resident and fellow education, basic and clinical research training, with particular strengths in diabetes and obesity, osteoporosis and disorders of mineral metabolism, neuroendocrine disorders, thyroid disorders and reproductive disorders.

Note to Editors: For additional comment on this study, please contact one of the following: Susan Greenspan, M.D., professor, divisions of endocrinology and geriatric medicine, department of medicine, University of Pittsburgh; and director, Osteoporosis Prevention and Treatment Center; 412-647-3555; Cliff Rosen, M.D., president of the American Society of Bone and Mineral Research, 207-262-1176; Joan Goldberg, executive director of the Society, 207-262-1176; or John Bilezikian, editor of the Journal of Clinical Endocrinology and Metabolism, 212-305-6238.

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