The effect of conjugated equine estrogen on diabetes incidence: The Women’s Health Initiative randomized trial

January 2006

Findings Summary

Diabetes Mellitus is a disease of elevated blood sugar. It is caused by an inability to get sugar from the blood stream into cells, either because the body does not produce insulin, the hormone that helps sugar get into the cells, or because the body cannot use the insulin produced correctly. Over 9 million women in the United States have diabetes and the number of women diagnosed each year is increasing. Diabetes has many complications associated with it, including heart disease, kidney failure, visual difficulties, and decreased sensation. Because of the large number of health problems associated with diabetes, it is important to find a way to prevent the disease.
Previous studies, including the WHI, have shown that women who take Estrogen plus Progesterone after menopause develop diabetes at a lower rate than women who do not take combined hormones. To see if this is true in women who take Estrogen alone, investigators examined the data from WHI trial of estrogen alone. Participants in WHI were asked every 6 months if their doctor had prescribed pills or insulin to treat diabetes. The number of new case of diabetes in those women taking estrogen pills was compared to those taking placebo tablets. These findings have been published in the January 2006 issue of the scientific journal Diabetologia. In summary:
  • A slightly smaller number of women who took Estrogen alone developed diabetes but it was not significant when statistical testing was done
  • 8.3% (397 cases/4787 women assigned to E alone) of women who took Estrogen alone developed diabetes over the course of the trial compared to 9.3% (455 cases/4887 women assigned to placebo) of women who took placebo
  • Blood sugar and insulin levels were lower after one year in those women who took Estrogen alone
Although diabetes is an important health problem in postmenopausal women, WHI investigators do not feel that the effects of Estrogen alone on reducing the risk of diabetes are enough to outweigh the higher rate of stroke and blood clots. However, since this study shows that hormonal treatment can affect blood sugar, insulin and the development of diabetes, these outcomes should be looked at in future trials of postmenopausal hormone therapy.