Differential impact of conventional and low-dose oral hormone therapy (HT), tibolone and raloxifene on functionality of the activated protein C system

Anette L. Eilertsen; Sigurd Liestøl; Marie-Christine Mowinckel; H. Coen Hemker; Per-Morten Sandset

doi:10.1160/TH06-11-0632

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2007; 97(06): 938-943
DOI: 10.1160/TH06-11-0632

Blood Coagulation, Fibrinolysis and Cellular Haemostasis

Schattauer GmbH

Differential impact of conventional and low-dose oral hormone therapy (HT), tibolone and raloxifene on functionality of the activated protein C system

Anette L. Eilertsen

¹Department of Haematology Ullevål University Hospital Trust, Oslo, Norway

²Medical Clinic, Faculty Division Ullevål University Hospital, Oslo, Norway

,

Sigurd Liestøl

¹Department of Haematology Ullevål University Hospital Trust, Oslo, Norway

,

Marie-Christine Mowinckel

¹Department of Haematology Ullevål University Hospital Trust, Oslo, Norway

,

H. Coen Hemker

³Synapse BV, Cardiovascular Research Institute, Maastricht, The Netherlands

,

Per-Morten Sandset

¹Department of Haematology Ullevål University Hospital Trust, Oslo, Norway

²Medical Clinic, Faculty Division Ullevål University Hospital, Oslo, Norway

› Author Affiliations

Abstract

Summary

Recent studies have shown that hormone therapy (HT) is associated with an acquired resistance to activated protein C (APC). The aims of the present study were to evaluate a possible dose-response relationship and differential effects of different HT regimens on functionality of the APC system. Two hundred two healthy women were randomly assigned to receive treatment for 12 weeks with tablets containing either low-dose HT containing 1 mg 17β-oestradiol + 0.5 mg norethisterone acetate (NETA) (n=50), conventional-dose HT containing 2 mg 17β-oestradiol and 1 mg NETA (n=50), 2.5 mg tibolone (n=51), or 60 mg raloxifene (n=51). Normalized APC system sensitivity ratios (nAPCsr) were determined in plasma collected at baseline and after 12 weeks using a thrombin generation-based APC resistance test probed with either recombinant APC (rAPC) or thrombomodulin (rTM). NAPCsr increased in both the conventional- and low-dose HT groups, consistent with reduced sensitivity to APC. The increase was slightly more pronounced in the conventional-dose group, but the difference between the two HT groups was not statistically significant. The sensitivity to APC was only marginally altered in those allocated to tibolone. Consequently, tibolone showed a different phenotype as compared with the low-dose HT group. A small increase in nAPCsr with both rAPC and rTM was seen in the raloxifene-group, but the increase was less than in the low-dose HT group. Our findings indicate that oestrogen-progestin therapy induces an APC resistant phenotype, which may be related to dose, whereas tibolone and raloxifene only marginally alter the sensitivity to APC.

Keywords

Activated protein C - hormone therapy - tibolone - raloxifene - coagulation

Full Text

References

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