Major Gene Study Finally Proves that Human Hormones are Healthier than Horse Hormones and Synthetic Drugs for Women’s Breasts

For a long time now, women and their physicians have been in conversation about the question of whether estrogen causes breast cancer.

The Women’s Health Initiative study which was published in 2002 showed a very slight increase in breast cancer in women who were taking a combination of a horse estrogen and a synthetic progesterone.

The headlines of the newspapers around the world forgot to mention that it was horse estrogen that was being tested. Along with the horse estrogen women were given a synthetic chemical progesterone-like molecule which is completely different than human progesterone. This is called medroxyprogesterone and is a completely chemically created drug.

If one looks at the details of the Women’s Health Initiative, one sees that of the women taking the combination of horse estrogen and synthetic progesterone, there were 38 women diagnosed with breast cancer per 10,000 women per year, compared to 30 cases diagnosed in women who were not using the hormone replacement therapy. The statistics that are given is that this is a 26% increase (because if you divide 38 by 30 you get 26% additional .) However, if you look at it as noted above it’s really an extra 8 women per 10,000 women who got cancer. This number does not sound as big as the number 26%. And again this was with a horse’s estrogen and drug form of progesterone!

When we look at the horse hormones in the estrogen used in this study, we see that they are called equilin and equiline. In at least one study equilin has been shown to be metabolized into a molecule which is a very potent cytotoxin. A cytotoxin is a molecule that is toxic to cells and can degenerate them to become cancer.

When integrative doctors, including myself, were asked about this study when it first came out, we pointed out that the estrogen used was from horses. Although there was one human estrogen in the estrogen combination used in the study, the other estrogens in the hormone, called equilin, and equiline, are only found in horses,. We also pointed out that the horse estrogens were much stronger stimulators to the breast tissue than human estrogen. In addition we would always remind people that the synthetic progesterone used in the study was a synthetic drug and was not human progesterone.

Gynecologists and oncologists have always been skeptical that there was any difference in the effect on breast tissue, between horse estrogen and a synthetic type of progerstone, than human estrogen and progesterone would have.

Now I am happy to tell you that a major presentation at the International Menopause Society has shown for the first time, proof of what hormone replacement therapy actually does to the genes involved in breast cancer.

The study that was done at the Karolinska Institute in Sweden found 30 healthy women volunteers who agreed to have two biopsies of their breast using a needle technique.

Breast tissue was taken from the group of women and the activity of 16 genes that were known to be associated with a greater risk of breast cancer were evaluated. The women were then divided into two groups.

One group took the conjugated horse estrogen and the synthetic progesterone, both of which were used in the Women’s Health Initiative study noted above.

The other group of 15 women were given human estrogen gel and oral capsules of human progesterone.

The women went through two cycles of the hormone replacement therapy and then had their second breast needle biopsies.

What was found in the biopsy analysis is that the horse estrogen and chemical progesterone combination changed the expression of 8 out of 16 of the breast cancer genes. In the women who took the human estrogen and human progesterone, only 4 out of the16 genes changed their expression. This difference was certainly statistically significant.

What does this mean?

Professor Gunnar Soderqvist, the lead author of the study stated ““Until now, it has not been possible to assess breast gene regulation in healthy women in vivo. This is the first study ever describing effects in healthy women during these HRT treatments and shows very important differences mostly in favour of ”natural“ treatment with the gel containing estradiol/ oral micronised progesterone when compared with ”synthetic” oral CEE/MPA. (horse estrogen and chemical progesterone).

He went on to say “The study does not show that either HRT formulation ”causes cancer,” but it does show that the type of HRT and perhaps the route of administration will cause differences in genes associated with breast cancer.

“We can conclude by saying that natural treatment with the estrogen gel and oral progesterone affects gene regulation and surrogate markers for breast cancer risk (such as mammographic density and breast cell proliferation) considerably less than the conventional synthetic treatment which stopped the WHI study.”

In addition, the president of the International Menopause Society, Professor Rod Baber said that “This very important study shows that use of HRT combining a transdermal estradiol preparation with oral micronised progesterone causes significantly less expression of genes associated with breast cell proliferation and breast cancer than the more traditional HRT combination of conjugated estrogens plus medroxyprogesterone.

“The basic science from this study supports the evidence we have from clinical trials such as the French E3N trial, which shows that the choice of estrogen and progestogen and the mode of delivery is important in reducing any risk of breast cancer possibly associated with long term HRT”

I am so delighted that this study has recently been published. Hopefully it will encourage doctors to give women who choose to take homone replacement therapy the natural bio-identical type of hormone replacement, rather than the horse and synthetic hormones which are still so widely used today.

When I look at the bottom line of this study in the perspective of time, I am so disappointed that it took scientists until 2014, using genomic testing only recently available, to figure out that naturally occurring human hormones would have less effect on a woman’s breast than horse estrogen and a synthetic drug.

I look forward to being in conversation with all of you about this.


For the first time, proof of what hormone replacement therapy does to genes involved in breast cancer

WHI Trial Suggests Possible Reduction in Breast Cancer Risk with Estrogen Alone

Hormone Replacement Therapy (HRT)

WHI Updated Analysis: No Increased Risk of Breast Cancer with Estrogen-Alone


Equilin Breakdown


About Dr. Soram Khalsa

As an MD, Dr Soram specializes in Integrative Medicine combining diet, nutrition, acupuncture, herbs and nutrition. Visit Dr Soram’s Healthy Living Store where you’ll find high-quality nutritional supplements: