Synthetic progesterone taken for therapeutic purposes such as dysfunctional uterine bleeding may increase the risk of heart disease, according to new data.

The new information comes from the snappily titled WHO Collaborative Study of Cardiovascular Disease (CVD) and Steroid Hormone Consumption (SHC). The researchers were working on the basis that the risk of heart disease with injectable progestogen has already been established.

In this multinational hospital based study, researchers looked at women aged 20 to 49 years who reported a first episode of either venous thromboembolism (VE), stroke or serious heart attack during the six year study period.

Each woman in the study group was matched with up to three comparable controls. Results showed that the greatest risk for therapeutic progestogens users was for venous thromboembolism.

The researchers point out that the women in this group were older, tended to be heavy cigarette smokers and also

to have a family history of cardiovascular disease. Nevertheless, even after adjusting for these factors, the results did not alter significantly. Women taking therapeutic progestogen still had nearly six times the risk of VE than non users (Lancet, 1999; 354: 1610). This risk is similar to that which has been reported for combined oral contraceptives, but greater than previously reported figures for progestogen only contraceptives. The risk of progestogen users developing stroke or heart disease was not significantly different than that of non users.

Progestogen preparations used for therapeutic purposes can differ from that used in oral contraceptives in several ways. For instance, there may be different progestogens, or they may be in substantially larger doses.