Norethisterone acetate alters coagulation gene expression in vitro in human cell culture.

INTRODUCTION: Both oestrogen and progestin and the route of administration have been implicated in cardiovascular and thromboembolic risk in post menopausal hormone users. Transdermal preparations have been reported as safer indicating that liver derived metabolites of oestrogen may be important. The aim of our study was to investigate the in vitro effects of 17ß-estradiol, its metabolites, and norethisterone acetate (NETA) on the expression of coagulation genes in cultured human cells. METHODS: Human hepatocytes and human umbilical vein endothelial cells(HUVECS) were treated with 17ß-estradiol, estrone, 2-hydroxyestradiol (2-OH), NETA and NETA/17ß-estradiol (10nM) for 24hours. Fibrinogen, factor VII, prothrombin and plasminogen activator inhibitor -1 (PAI-1) mRNA expression was determined in hepatocyte cultures using TaqMan PCR. Tissue factor (TF), tissue factor pathway inhibitor (TFPI), tissue plasminogen activator (tPA) and PAI-1 expression was determined in HUVECS. Expression of estrogen receptors was also determined. RESULTS: Fibrinogen and factor VII mRNA expression was upregulated 2-4 fold by estradiol and estrone. Addition of NETA downregulated fibrinogen and prothrombin. PAI-1 expression in hepatocytes was upregulated by estrone, 2-OH, NETA and NETA/17ß-estradiol. In HUVECS, TF, TFPI and PAI-1 expression was upregulated by estrone but not by 17ß-estradiol. NETA upregulated TF, TFPI and tPA expression. Estrogen receptor status was unaffected by the addition of NETA. CONCLUSIONS: This data suggests a role for progestins in modifying the effects of oestrogen and its metabolites on coagulation gene expression which may contribute to the reduced thrombotic risk associated with transdermal preparations.

Haemostatic activation in post-menopausal women taking low-dose hormone therapy: less effect with transdermal administration?

Hormone therapy (HT) increases the risk of cardiovascular and thromboembolic disease in post-menopausal women. Recent studies have suggested that prothrombotic mechanisms are likely to be involved. Transdermal HT avoids the first-pass effect of oestrogen in the liver and may have a less marked effect on the haemostatic system than equivalent oral preparations. The majority of studies have compared HT preparations that have different formulations as well as routes of administration. We investigated changes in the haemostatic system in post-menopausal women using two pharmacologically similar HT preparations, which differed only in their route of administration. Three hundred forty-four healthy post-menopausal women were randomised to six months treatment with either a transdermal matrix patch containing 25 microg 17beta-estradiol/125 microg norethisterone acetate (NETA) applied every 3-4 days, or an equivalent oral preparation (estradiol 1 mg and NETA 0.5 mg given once daily). Oral treatment significantly reduced fibrinogen (p < 0.003), factor VIIc (FVIIc) (p < 0.00001), and antithrombin (AT) levels (p < 0.005); the effects in the transdermal group were less marked with no reduction in fibrinogen levels and lesser effect on FVIIc (p < 0.03) compared with oral treatment. Treatment type significantly affected fibrinolysis with lower plasmin-anti-plasmin (PAP) levels in the transdermal group (p < 0.003) and lower plasminogen activator inhibitor-1 antigen (PAI-1) (p < 0.012) and tissue plasminogen activator (tPA) antigen levels in the oral group (p < 0.002). Prothrombin fragment 1.2 and activated protein C (APC) resistance were not affected by either treatment. Transdermal HT has a less marked effect on coagulation than an equivalent oral preparation. Randomised trials are required to investigate whether this translates into less risk of cardiovascular and thromboembolic disease.