For decades, fear has surrounded HRT. Use went from 26.9% of menopausal women in 1999 to 4.7% in 2020. All because of the Women’s Health Initiative – but the scare turned out to be unfounded. Here’s what happened:
The WHI was supposed to study many diseases in a large group of older women, particularly looking at proving that HRT helps protect women from heart disease. With over 161,000 women it promised to give us real data to support what many of us thought was true. In July 2002 the researchers held a press conference to say they were stopping the study early, because they had actually seen a small increase in heart attacks, strokes and – scariest to many women – breast cancer. Millions of women stopped their hormones, preferring to suffer. Physicians scrambled to help patients understand the results – especially since they didn’t release the actual study right away so we didn’t know what it actually showed!
When we did get access to the study, here is what it showed:
The wrong group was studied. Recruitment for studies is really hard, and it turned out they weren’t able to recruit enough women in their perimenopausal and early menopausal years. Instead they applied the results from older women to all groups. When the results for cardiovascular disease were teased out for the younger women, these results did not hold up.
The progestin used isn’t commonly used for HRT anymore. The group of women taking a combination of both estrogen and progestin (necessary if you still have a uterus) saw a slight increase of 26% relative risk for invasive breast cancer. While this sounds like a lot, this translates into 8 more cases per 10,000 woman years, slightly more risk than 1 glass of wine daily but less risk than 2 glasses of wine daily. In the age 50-59 yo group the increase was 6 additional cases per 10,000 woman years. Diagnosis was increased but deaths from breast cancer were NOT increased.
The estrogen only arm (Premarin) saw a decrease in both the risk of breast cancer diagnosis and mortality. Let that sink in – no increased risk of breast cancer with estrogen alone, in fact a decrease!
Next post: absolute risks of HRT/ERT from the WHI. Teaser: women who took hormones were less likely to die – from any cause.