Increase in stroke risk halts WHI estrogen-only arm: no increased breast cancer risk: data not fully analyzed; experts say no need to change clinical practice yet.(Women's Health Initiative)

The National Institutes of Health has discontinued the estrogen-only arm of its Women's Health Initiative study 1 year early, citing an increase in the risk of stroke in women taking the study medication.

Although the full results have not yet been released, the NIH said the increase was comparable to the 41% increased relative risk of stroke observed in the WHI combination hormone therapy (HT) arm (29 strokes per year vs. 21 per year for women taking placebo).

The strokes in the estrogen-only arm occurred over a range of ages--a pattern also seen in the combination HT study, which was also halted early, in 2002.

The use of estrogen only was associated with a decrease in the risk of hip fracture, but that protective effect was not deemed robust enough to balance the increased risk of stroke. Estrogen …