Effect of oral and transdermal estrogen replacement therapy on hemostatic variables associated with venous thrombosis: a randomized, placebo-controlled study in postmenopausal women.

OBJECTIVE: The purpose of this study was to investigate whether the effect of transdermal estrogen therapy in postmenopausal women differs from that of oral therapy with regard to resistance to activated protein C (APC), an important risk factor for venous thrombosis, and levels of related proteins, such as protein S, protein C, and prothrombin. METHODS AND RESULTS: In a randomized, double-blind, placebo-controlled study, 152 healthy hysterectomized postmenopausal women received daily either placebo (n=49), transdermal 17beta-estradiol (E2) 50 microg (tE2 group, n=33), oral E2 1 mg (oE2 group, n=37), or oral E2 1 mg combined with gestodene 25 microg (oE2+G group, n=33) for 13 28-day treatment cycles, followed by 4 cycles of placebo for each group. Plasma samples were collected at baseline and in cycles 4, 13, and 17. In cycle 13, significant increases versus baseline and placebo were found in normalized APC sensitivity ratios (nAPCsr) in all treated groups (tE2, +26.9%; oE2, +102.7%; oE2+G, +69.9%). Increases in nAPCsr were significantly higher in the oral treatment groups than in the tE2 group. In addition, compared with baseline and placebo, after 13 cycles, decreases were observed in total protein S (tE2, -4.1%; oE2, -7.9%; oE2+G, -5.8%), free protein S (tE2, -7.1%; oE2, -8.4%; oE2+G, -5.2%), and protein C in the oE2+G group (-6.4%), but these changes did not explain the increase in nAPCsr. Changes in prothrombin were small and also did not affect the nAPCsr. CONCLUSIONS: Increases were observed in resistance to APC, which were more pronounced in the oral treatment groups than in the transdermal group. The increase in resistance to APC was not explained by changes in protein S, protein C, or prothrombin and may contribute to the increased incidence of venous thrombosis in users of hormone replacement therapy.

Effect of hormone replacement therapy on plasma levels of the cardiovascular risk factor asymmetric dimethylarginine: a randomized, placebo-controlled 12-week study in healthy early postmenopausal women.

In a prospective, randomized, placebo-controlled 12-wk study, we investigated the effect of oral hormone replacement therapy on asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), and an independent risk factor for coronary heart disease. The effects on arginine and symmetric dimethylarginine were also investigated. Sixty healthy early postmenopausal women received daily placebo (n = 16) or oral 17beta-estradiol 2 mg, either unopposed (E(2); n = 16) or sequentially combined with dydrogesterone 10 mg (E(2)+D; n = 14) or trimegestone 0.5 mg (E(2)+T; n = 14). ADMA levels reduced in all active treatment groups. Compared with baseline and placebo, the largest reduction in ADMA levels was observed in the E(2)+T group [-18.7% (95% confidence interval [CI], -25.4 to -11.9%) and -21.1% (95% CI, -26.2 to -16.1%), at 4 and 12 wk, respectively]. At 4 and 12 wk in the E(2)+T group, arginine levels were significantly reduced as well [-30.9% (95% CI, -41.1 to -20.7%) and -36.3% (95% CI, -43.1 to -29.5%), respectively], whereas symmetric dimethylarginine levels were significantly lower in the E(2)+D group after 12 wk [-11.6% (95% CI, -19.9 to -3.3%)]. In conclusion, unopposed oral estradiol and estradiol combined with dydrogesterone or trimegestone reduced plasma levels of the NOS inhibitor ADMA. Whether the reduction of the NOS substrate arginine in the E(2)+T group counteracts the potentially beneficial effect of ADMA reduction or reflects increased NO production remains to be investigated.

Increased resistance to activated protein C after short-term oral hormone replacement therapy in healthy post-menopausal women.

As hormone replacement therapy is associated with an early excess risk of venous thrombosis, we investigated the effect of different oral hormone replacement therapies on resistance to activated protein C, and on levels of factor VIII antigen (FVIII:Ag) and factor XI antigen (FXI:Ag). In a prospective, randomized, placebo-controlled 12-week study, 60 healthy post-menopausal women daily received either placebo (n = 16) or 2 mg of micronized 17beta-oestradiol, either alone (E2, n = 16) or sequentially combined with dydrogesterone 10 mg (E2 + D, n = 14) or trimegestone 0.5 mg (E2 + T, n = 14). Medication was given orally. Normalized activated protein C sensitivity ratios (nAPCsr) were determined by quantifying the effect of activated protein C on the endogenous thrombin potential. FVIII:Ag and FXI:Ag were determined by enzyme-linked immunosorbent assay. Compared with baseline and placebo, the nAPCsr increased (92% to 142%; all P < 0.001) in all active treatment groups after both 4 and 12 weeks. Compared with placebo, hormone replacement therapy was not associated with significant changes in FVIII:Ag. After 4 and 12 weeks, FXI:Ag levels were significantly decreased in the E2 group (mean percentage changes from baseline versus placebo: -15.0%, P = 0.001 at 4 weeks and -16.6%, P = 0.003 at 12 weeks) and in the E2 + D group (-10.4%, P = 0.02 and -10.4%, P = 0.02). In conclusion, all hormone replacement regimens were associated with a large increase in resistance to activated protein C. In contrast, hormone replacement therapy had no effect on FVIII:Ag. Oral E2 and E2 + D had a small, favourable effect on FXI:Ag.

Effects of low-dose oral and transdermal estrogen replacement therapy on hemostatic factors in healthy postmenopausal women: a randomized placebo-controlled study.

OBJECTIVE: This study was undertaken to investigate the effect of transdermal and oral estrogen replacement therapy in healthy postmenopausal women on markers of coagulation and fibrinolysis associated with coronary artery disease. STUDY DESIGN: In a randomized, placebo-controlled, double-blind study, healthy hysterectomized postmenopausal women received daily either placebo (n=49), transdermal 17beta-estradiol (E(2)) 50 microg (tE(2) group, n=33), oral E(2) 1 mg (oE(2) group, n=37), or oral E(2) 1 mg combined with gestodene 25 microg (oE(2)+G group, n=33) for thirteen 28-day treatment cycles. Hemostatic variables were measured in blood samples collected at baseline and in cycles 4 and 13. RESULTS: No significant changes versus baseline and placebo were found in the tE(2) group, except for plasminogen activator inhibitor type-1 (PAI-1) in cycle 13 (-32.4%, P=.01). In the oE(2) group, significant percentage changes from baseline versus placebo in cycle 13 were found in fibrinogen, -5.4% (P<.05); factor VII, -7.3% (P<.05); thrombin-antithrombin III complexes, -13.3% (P<.05); tissue-type plasminogen activator (t-PA), -17.3% (P<.001); and PAI-1, -54.3% (P<.001). In the oE(2)+G group, respective changes were factor VII, -17.6% (P<.001); t-PA, -14.5% (P=.01); PAI-1, -36.4% (P<.01); and D-dimer, +21.8% (P<.05). No significant changes were observed in prothrombin fragment 1+2 and plasmin-alpha(2)-antiplasmin complexes. CONCLUSION: Low-dose oral estradiol therapy was associated with an increase in fibrinolysis and small decreases in procoagulant variables. Transdermal therapy had minor effects.