Effect of Estrogen Plus Progestin on the Incidence of Diabetes in Postmenopausal Women

July 2004

Findings Summary

Approximately 9.3 million (8.7%) of all women over the age of 20 in the U.S. have diabetes, according to the American Diabetes Association. Diabetes is a disease in which the body does not produce or properly use insulin, a hormone needed to convert sugar, starches and other food into energy. Diabetes is the fifth-deadliest disease in the U.S., and it has no cure. Because of the increasing lifespan of women, the larger percentage of women who are overweight and the rapid growth of minority populations, the number of women at high risk for diabetes and its complications is increasing.
WHI researchers wanted to investigate whether estrogen plus progestin (E + P) might affect women’s risk of developing diabetes. The investigators learned about new cases of diabetes in WHI participants by asking the women every six months if they had just started being treated with pills or insulin for diabetes. The data from this part of the study have now been analyzed and appear in the July 2004 issue of the medical journal, Diabetologia.
The results showed that fewer women taking E + P developed diabetes compared to those taking placebo (inactive) pills. After an average of 5.6 years, 277 of the 8,014 women taking E + P (3.5%) and 324 of the 7,627 women taking placebo (4.2%) developed treated diabetes. From these cases, we learned:
  • Overall, E + P reduced the risk for newly treated diabetes by 21%. So for every 10,000 women taking E + P, there were 15 fewer cases of diabetes per year.
  • E + P produced a small decrease in glucose (blood sugar) and insulin levels in the blood after one year in the study, which may have been the reason for the lower rate of diabetes in this group.
  • Although E + P slightly reduced weight and waist size in women after one year in the study, this was not a major factor in the lower diabetes rate.
Although diabetes is an important health problem in postmenopausal women, WHI investigators do not feel that the effects of E + P on reducing the risk of diabetes are enough to outweigh the higher rate of breast cancer, heart attacks, 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.
Women in this trial were randomly assigned to either placebo or estrogen plus progestin (conjugated equine estrogens 0.625 mg and medroxyprogesterone acetate (2.5 mg), also known as Prempro). When the WHI study first began, this was the most commonly prescribed menopausal hormone therapy in the United States for women with the uterus. Because of the overall findings of health risks exceeding benefits, use of these hormones is now generally recommended only for short-term relief of menopausal symptoms.