Hormone therapy and risk of venous thromboembolism among postmenopausal women

There is now growing evidence that VTE risk among HT users strongly depends on the route of administration. Indeed, transdermal estrogens, unlike oral estrogens, are not associated with an increased VTE risk and biological data support this difference between oral and transdermal estrogens. In addition, transdermal estrogens may not confer additional risk in women at high risk of VTE. Significant differences in thrombotic risk between HT preparations also relate to the concomitant progestogen. Studies have consistently shown that VTE risk is higher among users of combined estrogens plus progestogens than among users of estrogens alone. With respect to the different pharmacological classes of progestogens, two observational studies found that norpregnane derivatives are associated with an increased VTE risk, whereas micronized progesterone may be safe with respect to thrombotic risk. In conclusion, transdermal estrogens alone or combined with micronized progesterone may represent the safest alternative for women who require HT.