Short answer: In large trials it did not raise diabetes rates. In the Women's Health Initiative, fewer women developed treated diabetes on estrogen plus progestin (3.5% vs 4.2% on placebo), and estrogen alone showed a smaller drop that was not statistically significant (8.3% vs 9.3%). Even so, estrogen labels list impaired glucose tolerance and say estrogen can make diabetes worse, so blood sugar is watched in women who already have it.
| Trial | Women | Treatment | New diabetes |
|---|---|---|---|
| WHI estrogen plus progestin (Margolis 2004) | 15,641 aged 50 to 79 with a uterus, 5.6 years | Conjugated estrogens 0.625 mg plus medroxyprogesterone 2.5 mg a day, or placebo | 3.5% vs 4.2% (hazard ratio 0.79) |
| WHI estrogen alone (Bonds 2006) | 10,739 aged 50 to 79 after hysterectomy, 7.1 years | Conjugated estrogens 0.625 mg a day, or placebo | 8.3% vs 9.3% (hazard ratio 0.88, not statistically significant) |
| HERS (Kanaya 2003) | 2,029 women with heart disease and no diabetes, 4.1 years | Conjugated estrogens 0.625 mg plus medroxyprogesterone 2.5 mg a day, or placebo | 6.2% vs 9.5% (relative hazard 0.65) |
Both WHI analyses also found that insulin resistance fell in the first year on hormones. In the estrogen-alone trial, that difference was gone by years 3 and 6. In HERS, fasting glucose rose on placebo but did not change on hormone therapy.
WHI counted diabetes by self-reported treatment with insulin or diabetes pills, so untreated cases were missed. All three trials used one older combination, oral conjugated estrogens with or without medroxyprogesterone, so they do not show what patches, gels or other progestogens do.
The trial teams were clear about what the results do not support. The WHI estrogen-alone authors wrote that conjugated estrogens should not be used to prevent diabetes because of their known risks, and the HERS authors said the finding was not enough to recommend hormones for that purpose. Hormone therapy is prescribed for menopause symptoms, and its other risks are weighed with the prescriber.
The Premarin and estradiol tablet labels list impaired glucose tolerance among the effects of estrogens on lab tests. Premarin lists glucose intolerance among side effects reported after approval, and its patient information mentions changes in lab results such as high blood sugar. Both labels say estrogen may make diabetes worse and should be used with caution in women who have it.
Insulin labels such as Humalog list estrogens, oral contraceptives and progestogens among medicines that may weaken insulin's blood sugar lowering effect, and say more frequent glucose checks or dose changes may be needed when they are taken together.
For a woman on insulin or diabetes pills, starting, stopping or changing hormone therapy is a time when blood sugar can shift either way. Whether and how often to check more is up to the prescriber. Dose Track can log hormone doses next to glucose readings, so changes line up on one timeline.
Read more on Dose Track: Women's Health Initiative · Menopause · Premarin side effects · Insulin resistance