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(Stroke. 2002;33:2700.)
© 2002 American Heart Association, Inc.

Original Contributions

Comparison of Tibolone and Conjugated Equine Estrogens Effects on Carotid Artery Atherosclerosis of Postmenopausal Monkeys

Thomas B. Clarkson, DVM; Mary S. Anthony, PhD; Tomi S. Mikkola, MD, PhD Richard W. St Clair, PhD

From the Comparative Medicine Clinical Research Center (T.B.C., M.S.A.) and Department of Pathology (T.S.M., R.W.S.C.), Wake Forest University School of Medicine, Winston-Salem, NC. Current address of T.S.M. is Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Helsinki, Finland.

Correspondence and reprint requests to Thomas B. Clarkson, DVM, Comparative Medicine Clinical Research Center, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157-1040. E-mail tclarkso{at}wfubmc.edu

Background and Purpose— Tibolone is a tissue-specific compound that has favorable effects on bone and menopausal symptoms without stimulating endometrium or breast, but lowers concentrations of plasma high-density lipoprotein (HDL) cholesterol (HDLC). This study was designed to determine whether the HDL lowering with tibolone exacerbated common or internal carotid artery atherosclerosis and to evaluate tibolone treatment relative to conjugated equine estrogens (CEE) alone or in combination with medroxyprogesterone acetate (MPA).

Methods— Carotid artery atherosclerosis was compared in groups of surgically postmenopausal cynomolgus monkeys treated with CEE, CEE+MPA, or either of 2 doses of tibolone versus untreated monkeys.

Results— Despite a 30% to 52% lowering of HDLC with tibolone, there was no significant effect on carotid artery atherosclerosis. CEE and CEE+MPA, however, inhibited carotid artery atherosclerosis by 60%.

Conclusions— In surgically postmenopausal cynomolgus monkeys, CEE and CEE+MPA inhibited common and internal carotid artery atherosclerosis. Despite the potentially adverse effects of tibolone on HDLC, tibolone did not exacerbate atherosclerosis.

Key Words: carotid atherosclerosis • conjugated equine estrogens • hormone replacement therapy • tibolone • monkeys

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