Reproduced by permission of the VOICE, DES Action USA Spring 2009 #120

“Hypermethylation of HOXA 10 by in utero diethylstilbestrol exposure: an epigenetic mechanism for altered developmental programming,”

Hugh S. Taylor, et al, Endocrinology, March 19, 2009 as doi:10.1210/en.2009-0071

Reviewed by Fran Howell

We know of the havoc caused by DES when introduced to a developing fetus: abnormalities of the female and male reproductive tracts, infertility problems, and cancers of the vagina, cervix and breast, among other health issues. Now researchers at the Yale School of Medicine are zeroing in on why DES acts the way it does.

The team, led by Hugh S. Taylor, M.D., professor in the Department of Obstetrics, Gynecology and Reproductive Science, exposed pregnant mice to DES and studied their female offspring.

He was particularly interested in the HOX gene family, which regulates development. One in particular, The HOXA10 gene directs embryonic uterine development.

Earlier studies by Taylor and others have shown that prenatal DES exposure alters the process called methylation. That is how genes are switched on and off at certain times to do what they are programmed to do. The genes themselves are not changed or mutated, but rather, the way they function or express themselves is altered. DES was known to disrupt the process, but it wasn’t understood exactly how.

Taylor focused on the HOXA10 genes from DES Daughter mice because they act as important regulators of tissue identity. Alterations in HOX gene expression cause abnormalities in tissues that depend on those genes for proper development.

According to Taylor, altered gene expression, or methylation, has been associated with reproductive tract abnormalities, such as those seen in DES Daughters and Sons, along with human cancers in adulthood. This research examined how HOXA10 gene expression is altered by in utero DES exposure.

What he learned is that in utero exposure to DES results in methylation of the HOXA 10 gene, causing it to be lower in areas where it is normally required for uterine development and higher in areas where it should not be expressed. One of these areas is the vagina. This finding perhaps explains the vaginal adenosis common in DES Daughters; The HOXA 10 gene is more active than it should be during development of the fetus. Reproductive tract abnormalities experienced by many DES Daughters are now suspected to be the result of lower or higher functioning of this gene.

Also noted is that the DES-caused hypermethylation of the HOXA10 gene in utero does not cease after birth. Taylor found that prenatal DES exposure “results in lasting changes in gene expression, persisting well after exposure, into adulthood.” This helps explain why developing fetus exposed to DES might develop cancers and other health issues many years after exposure.

By zeroing in on how prenatal exposure to DES causes the hypermethylation of certain genes, scientists are moving forward with a better understanding of why DES causes the problems it does, both at the time of exposure and also decades later.

Did You Know ? <> DES Was Never Banned For Human Use

Time To Set The Record Straight

In 1971, after DES Daughters were diagnosed with a rare cancer, the FDA told doctors to stop prescribing DES to their pregnant patients. But the drug was NOT banned for human use.

Some doctors did not get the message, while others chose to ignore it. We are now learning of cases in which DES was prescribed well past 1971 in the USA and also into the 1980s internationally.

Of note is that back in 1959, DES was banned from animal feed given to chickens and lambs after high DES levels produced side effects. They included male breast growth in humans who worked with these animals. But DES prescriptions continued being written for women!

It wasn’t until September 30, 2000, that the FDA finally withdrew its approval of DES for humans. By then, no doctors were prescribing it anyway. But DES was NEVER BANNED for human use, despite what you may have heard!

For more information on DES please see these links:


DES UK – Journal of a DES Daughter


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