The largest study analysing the relationship between hormone therapy and Venous thromboembolism (VT) is the Women’s Health Initiative (WHI), which included two large clinical trials. One WHI trial examined the effects of oestrogen plus progestin and found that this combination of hormones appeared to increase the risk of VT.

J. David Curb, M.D., University of Hawaii and Pacific Health Research Institute, Honolulu, and colleagues analysed data from the other WHI trial, in which the effect of oestrogen alone was studied in 10,739 women aged 50 to 79 years. The participants were randomly assigned to take either combined equine oestrogens or placebo. They were followed for an average of 7.1 years, during which 197 women developed VT, including 144 with deep vein thrombosis, 91 with pulmonary embolism and 38 with both.

Of those 197 women who developed VT, 111 were taking oestrogen and 86 were taking placebo. The risk of VT was slightly higher for women receiving oestrogen therapy; was significantly increased for deep venous thrombosis, but not significantly increased for pulmonary embolism; and was highest in the first two years of therapy. Overall, the risk of venous thrombosis associated with oestrogen therapy was lower than that associated with oestrogen plus progestin in the other WHI trial.

“Our data suggest that although the absolute incidence is relatively low, the use of combined equine oestrogens increases the relative risk of venous thrombosis in postmenopausal women without a uterus,” the authors conclude. “Women with appropriate indications, such as short-term treatment of severe menopausal symptoms, should use combined equine oestrogens only after careful consideration of the relative risks and benefits, especially if the women have other risk factors for venous thrombosis.”

MEDICA.de; Source: American Medical Association (AMA)