TY - JOUR
T1 - Differential impact of conventional and low-dose oral hormone therapy (HT), tibolone and raloxifene on functionality of the activated protein C system
AU - Eilertsen, Anette L.
AU - Liestol, Sigurd
AU - Mowinckel, Marie-Christine
AU - Hemker, H. Coen
AU - Sandset, Per-Morten
PY - 2007
Y1 - 2007
N2 - 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 17 beta-oestradiol + 0.5 mg norethisterone acetate (NETA) (n=50), conventional-dose HT containing 2 mg 17 beta-oestradiol and I 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.
AB - 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 17 beta-oestradiol + 0.5 mg norethisterone acetate (NETA) (n=50), conventional-dose HT containing 2 mg 17 beta-oestradiol and I 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.
U2 - 10.1160/TH06-11-0632
DO - 10.1160/TH06-11-0632
M3 - Article
SN - 0340-6245
VL - 97
SP - 938
EP - 943
JO - Thrombosis and Haemostasis
JF - Thrombosis and Haemostasis
IS - 6
ER -