A.L. Eilertsen

Mechanisms of thrombosis related to hormone therapy

Combined oral contraceptives and combined oral postmenopausal hormone therapy are associated with a weak, but clinically significant risk of arterial and venous thrombosis (VT). The effects are related to dose of estrogen and type of progestin. The main effects are increase in markers of activated coagulation, reduction in coagulation inhibitors, and acquired activated protein C resistance. Reduction in tissue factor pathway inhibitor (TFPI) is probably an important mechanism, which predicts activation of coagulation and acquired resistance to activated protein C. Coagulation markers should be used as intermediate or surrogate markers in early pharmacodynamic studies to evaluate the risk associated with new formulations.

Differential impact of conventional-dose and low-dose postmenopausal hormone therapy, tibolone and raloxifene on C-reactive protein and other inflammatory markers.

Summary.  Background: Postmenopausal hormone therapy (HT) is associated with an increased risk for arterial and venous thrombosis. Objectives: To compare the impact of HT, tibolone, and raloxifene on C‐reactive protein (CRP) and other inflammatory markers, and to investigate possible underlying mechanisms for changes in CRP and D‐dimer. Methods: Two hundred and two healthy women were randomly assigned to treatment for 12 weeks with either low‐dose HT containing 1 mg of 17β‐estradiol and 0.5 mg of norethisterone acetate (NETA) (n = 50), conventional‐dose HT containing 2 mg of 17β‐estradiol and 1 mg of NETA (n = 50), 2.5 mg of tibolone (n = 51), or 60 mg of raloxifene (n = 51). Results: CRP increased in the conventional‐dose HT and low‐dose HT groups. These changes were significantly more pronounced in the conventional‐dose HT group (rmanova,P = 0.02). Also, tibolone was associated with an increase in CRP, in contrast to raloxifene, which reduced CRP. Reductions in levels of Lp(a), intercellular adhesion molecule‐1 (ICAM‐1), P‐selectin, E‐selectin, monocyte chemotactic protein 1 (MCP‐1) and interleukin‐6 (IL‐6) were observed in all treatment groups. The changes were most pronounced for the conventional‐dose HT group, and least pronounced for the raloxifene group, whereas the changes in those allocated to tibolone and low‐dose HT were intermediary. Increased levels of tumor necrosis factor (TNF)‐α and von Willebrand factor (VWF) were seen in the raloxifene group. We observed positive associations between changes in IL‐6, VWF, MCP‐1, and CRP. Conclusions: The regimens had markedly different impacts on markers of inflammation. The average increase in CRP was not accompanied by increases in the average levels of IL‐6, TNF‐α or other markers, but women with large reductions in IL‐6 had reduced increases in CRP.

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

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.

Differential impact of conventional and low‐dose oral hormone therapy, tibolone and raloxifene on mammographic breast density, assessed by an automated quantitative method

Objective  To evaluate impact of different postmenopausal hormone therapy (HT) regimens and raloxifene on mammographic breast density.

Tissue factor pathway inhibitor polymorphisms in women with and without a history of venous thrombosis and the effects of postmenopausal hormone therapy

Postmenopausal hormone therapy is associated with marked reduction in tissue factor pathway inhibitor (TFPI) levels, and low TFPI levels have been associated with increased risk of venous thrombosis. Polymorphisms in the TFPI gene may affect the expression of TFPI. We aimed to investigate the influences of such polymorphisms on plasma TFPI levels and to investigate the effect of hormone therapy. Four single nucleotide polymorphisms in the TFPI gene (the −287T/C and the −399C/T polymorphisms in the 5′ upstream region, and the intron 7 −33T/C and the exon 9 874G/A polymorphisms) were studied with regard to frequency, phenotype, and their influence on hormone therapy in postmenopausal women with a history of venous thrombosis (n = 138), in healthy postmenopausal women (n = 202), and in normal controls (n = 212). The frequencies of the −287C and the −33C variants were nonsignificantly lower in cases than in controls, and the polymorphisms were associated with slightly higher levels of free TFPI antigen (−287C; P = 0.076) and higher TFPI activity (−33C; P < 0.001). The −399T variant showed equal distribution in cases and controls, but was associated with lower levels of TFPI activity (P = 0.036). Conventional-dose hormone therapy induced significant reductions in TFPI levels irrespective of genotypes. In healthy women treated with low-dose hormone therapy, the reduction in TFPI levels was less pronounced with the −287C variant (P = 0.054). Our study indicates that polymorphisms in the TFPI gene may be of importance for plasma TFPI levels and for the effects of hormone therapy.

A microarray study on the effect of four hormone therapy regimens on gene transcription in whole blood from healthy postmenopausal women

BACKGROUND Postmenopausal hormone therapy is associated with many diseases and conditions, e.g., cardiovascular diseases and asthma, but the underlying molecular mechanisms are incompletely understood. The aim of the current study was to investigate the effect of four different postmenopausal hormone therapy regimens on gene transcription. MATERIALS AND METHODS Twenty-four healthy postmenopausal women (six women in four groups) were randomly allocated to conventional-dose 17β-estradiol/norethisterone acetate (NETA), low-dose 17β-estradiol/NETA, tibolone, or raloxifene hydrochloride. RNA was isolated from whole blood before and after 6weeks of treatment. The changes in mRNA were assessed with a microarray chip. RESULTS The genes FKBP5, IL13RA1, TPST1, and TLR2 were up-regulated and among the most significantly changed genes in the groups treated with conventional-dose 17β-estradiol/NETA and tibolone. Up-regulation of TPST1 was associated with reduction of tissue factor pathway inhibitor in plasma. Nine biological pathways were associated with conventional-dose 17β-estradiol/NETA, most significantly the pathways for asthma, toll-like receptor signaling, cell adhesion molecules, and MAPK signaling. Transcriptional changes with false discovery rate below 0.10 were found in 10 genes in the conventional-dose 17β-estradiol/NETA group, 7 genes in the tibolone group, and zero genes in the women on low-dose 17β-estradiol/NETA. No genes or pathways were associated with raloxifene treatment. CONCLUSIONS The difference between low-dose and conventional-dose17β-estradiol/NETA indicates an effect of dose on transcriptional response. Several genes and pathways related to cell adhesion molecules and immunity related cell surface receptors were influenced by conventional-dose 17β-estradiol/NETA.

Hormone therapy and raloxifene reduce the coagulation inhibitor potential.

The coagulation inhibitor potential (CIP) assay may detect major thrombophilia at a sensitivity of 100% and a specificity of 70–80%. Subnormal CIP might be associated with increased risk of thrombosis. This study compared the effect on CIP in plasma samples from postmenopausal women treated with four different regimens. Fibrin aggregation in plasma was monitored after activation with tissue factor. The effect of potentiated inhibition of coagulation was measured. Plasma samples from 202 healthy women randomly assigned to receive treatment for 12 weeks with conventional-dose or low-dose hormone therapy, raloxifene or tibolone were examined. Major thrombophilias were excluded. Compared with baseline, the median level in CIP was reduced by 64% in the conventional-dose group, by 38% in the low-dose group and by 31% in the raloxifene group, whereas for those treated with tibolone the median CIP increased by 9%. The median changes in CIP were significant for both hormone therapy groups (P < 0.0001) and for the raloxifene group (P = 0.003), but not for the tibolone group (P = 0.653). The 12 women with heterozygous factor V Leiden mutation had a significantly reduced median CIP level (P < 0.0001) at baseline. Hormone therapy and raloxifene, associated with venous thromboembolism, reduce the CIP. Tibolone does not reduce the CIP.

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

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 17ss-oestradiol + 0.5 mg norethisterone acetate (NETA) (n = 50), conventional-dose HT containing 2 mg 17ss-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.