Journal / Women's Health Initiative

Women’s Health Initiative Study Summary

Nancy L. Belcher

Medically reviewed by Nancy L. Belcher Ph.D, MPA

Written by Winona Editorial Team

Last updated November 25, 2021

Women’s Health Initiative Study Summary

The Women’s Health Initiative study transformed how women age, and not necessarily for the better. The Women’s Health Initiative (WHI) originated in 1991 and lasted until 2005. It was a unique research study that enrolled more than 160,000 women throughout the US, my mother included. Data from the study was collected at the Fred Hutchinson Cancer Research Center where I was a research scientist for many years. The results of the WHI study negatively impacted the way doctors have prescribed hormone replacement therapy (HRT), and how women think about HRT, for 30 years!

The Women’s Health Initiative Study 

The original intention of the Women’s Health Initiative study was to create a large, inclusive women’s study that focused on strategies to prevent the major causes of death, disability, and frailty in women. The sheer size and breadth of the WHI opened the door for the exploration of research topics in women’s health and aging that had not been evaluated before. Kudos to those researchers for their determination to provide women with improving healthcare information as they age.

The Women’s Health Initiative continues to research women’s aging even today, and the WHI research team has revised its statement about the safety of HRT. Regarding HRT prescriptions available for menopause, the WHI team has revised their statements from 2005 to read, “Hormone therapy is an option for some women to help relieve symptoms that occur early in menopause”.1,2

In my opinion, the most detrimental impact of the WHI study was the inaccurate identification of a relationship between the use of estrogen therapy and the risk for heart disease, and breast cancer.3 These findings continue to be echoed over and over on the internet even though they are inaccurate, outdated and were reversed by the very researchers that released the findings.

Most women don’t know about the updated HRT research results and just read about, or hear from friends what the original, outdated study results reported. As a result, they unnecessarily fear HRT. The HRT treatment that Winona is providing in 2021 is vastly different from the estrogen used in the 30-year-old study. The WHI researchers used “conjugated equine estrogens extracted from pregnant horse urine,”  which is not prescribed by Winona. The name of the estrogen provided in the original WHI study was Premarin (PREgnant MAres uRINe). Yes, estrogen was derived from pregnant horse urine.

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Beyond using a type of estrogen that Winona does not prescribe, the WHI’s original research findings had many flaws.  For example, in order to study heart disease, researchers enrolled older women. Women who had been in menopause for as long as 30 years. Many had been hormone-deficient for decades. Some women in the study were nearly 80 years old.

We now know that if estrogen treatment is provided in a woman’s ’40s and 50’s the risk of heart disease will decrease. However, the WHI reported an increase in heart disease because of these much older women who had spent decades at very low estrogen levels, and therefore, the WHI conclusions were not accurate for younger women. 

Today we offer bioidentical estrogens and micronized progesterone that are made into a range of products, which are FDA-approved and available with a prescription. Winona’s bioidentical estradiol comes in several forms, including a pill, patch, and cream. Micronized progesterone comes in a capsule or as a cream.

There are many proven health benefits to hormone replacement therapy (HRT). We know that providing estrogen and progesterone HRT inhibits tumorigenesis (the development of tumors), and represents a strategy to prevent breast cancer.3

Data consistently shows that women on HRT can improve bone health, mood, wellness, and reduce cancer and mortality in the range of 30%.4,5,6 We also know that Winona HRT can offset many of the side effects of menopause including hot flashes, weight gain, skin dryness, sleeplessness, depression and so much more WITHOUT the risks identified in the original WHI study.  

Women’s Health Initiative Study Summary

Winona is here to provide each client with safe and effective individualized therapy for their menopause symptoms. As a scientist, working closely with our physicians, I am excited to say we have now come full circle. There is a clear, medically appropriate role for HRT in menopause health, symptom relief, and disease prevention.7,8

We encourage you to read more about the WHI HERE. As women, there is much to learn about our ever-changing bodies. Winona scientists have also provided you with a long list of scientific articles related to hormone treatments and your health, and a great facts sheet found HERE.

Nancy L. Belcher, Ph.D., MPA  |  CEO, Winona, Inc.

“This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.”






  5. J Womens Health 1997 Newton, KM

  6. Henderson, BE, Arch Intern Med,1991;151:75–78

  7. Chen, WY Arch Intern Med. 2006;166:1027–1032