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Striking New Study -- Thimerosal Threatens Males More

Male_femaleEditor's Note -- Sometimes the most important information comes from people who aren't even looking for it. Here is a case in point, brought to our attention by Dr. Mark Geier and David Geier. Three Canadian researchers were experimenting with Thimerosal on mice for reasons having nothing to do with the vaccine mercury-autism debate. But they stumbled across the fact that Thimerosal was three times more toxic to male rats than female rats -- "the first report of gender-selective toxicity of thimerosal." Given the way it mirrors the gender differences in autism, this is a huge deal, even if preliminary. Below is the Geiers' discussion of the study's significance and HERE is a link to the study itself. As our AOA colleague Mark Blaxill says, "the facts tend to cluster around a good hypothesis." -- Dan Olmsted
In this new study, "Gender-Selective Toxicity of Thimerosal" published in the peer-reviewed journal of Experimental and Toxicologic Pathology by Dr. Donald R. Branch of the Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, the investigator examined the sex-specific toxicity of Thimerosal in a mice model system.

This investigator described, "Thimerosal is an organic compound that contains mercury and has been used historically as a preservative in vaccines and pharmaceutical products. The breakdown product, ethylmercury, in thimerosal-preserved childhood vaccines has been suggested to be neurotoxic and to contribute to the etiology of neurodevelopmental disorders, including autism; however, this supposition is highly controversial."

The researchers were "doing an unrelated study that was testing only for the maximum tolerated dose (MTD) levels for thimerosal in a mouse model to be subsequently used in a study of reversal of immune-mediated platelet destruction (Rampersad et al., 2005). However, during our MTD studies, we serendipitously discovered that thimerosal shows a differential toxicity that depends upon whether the test animals are male or female."

This investigator then went on to describe, "An important consideration when trying to evaluate the possible role of thimerosal toxicity is that autism occurs approximately four times more frequently in males compared to females (MMWR, 2007). Thus, if males have an increased sensitivity to thimerosal, this would have to be taken into account with analyses of any outcomes. Our results that demonstrate a significant difference in the MTD of thimerosal depending upon whether the test animal is male or female is, thus, an important finding. Indeed, in mice, we found when using 10% DMSO to completely dissolve the thimerosal prior to injection that the MTD of thimerosal in males was only 25.6 mg/kg; whereas, in females, the MTD was 76.8 mg/kg. Thus, thimerosal has a 3-fold increased toxicity in males compared to females."

Further, he postulated, "Although the in vivo levels of thimerosal used in our studies are far higher than what would be expected in humans, this may not preclude the impact of our findings as we were using mortality as our outcome. Although our study is not extensive as the group sizes are small, nevertheless, we clearly found that male mice were more susceptible to the toxic effects of thimerosal than were female mice."

In addition, he stated, "recently, it has been argued that prenatal and neonatal testosterone exposures may be risk factors for autism (Knickmeyer and Baron-Cohen, 2006). Furthermore, it has been reported that estrogens are protective against neurotoxic effects (Wang et al., 2006) and may protect against certain neurodegenerative diseases, such as Parkinson's disease (Benedetti et al., 2001; Dean and McCarthy, 2007). Thus, our findings that thimerosal has increased toxicity in males compared to female mice suggest that estrogens produced in female mice may have some protective effect on the toxicity of thimerosal, while testosterone may have no effect or, perhaps, accelerate these toxic effects."

In conclusion, the investigator stated, "In summary, this is the first report of gender-selective toxicity of thimerosal. As autism occurs much more frequently in males than in females (MMWR, 2007), our findings may relate to a potential selectivity of thimerosal for toxic effects in some male children..."

Dr. Mark Geier
David Geier



news worthy or not, i love hearing about these things! and to just stumble upon it! i too had heard that people thought estrogen protects females. it's just one more study to use for oue battle!


I'm trying to understand why this piece continues to get "this is old news" comments when, in fact, this is not old news. The subject matter may have been discussed previously, and in different venues; however, THIS study/finding is new, hot off the presses news.

If researchers were trying to determine the effects of multiple vaccines on the length of a rat's tail, and inadvertently discovered that they had created a litter of autistic rat babies; would that be old news because we've all been talking about the effects of vaccines on our kids?

I'm not getting it. But then, I'm not the smartest bulb in the pack... and my coffee hasn't kicked in.

Please explain... go slow and simple for me, if you don't mind.


Even though this is "old" news for some of us, it is good to see others confirming what Dr. Boyd Haley has been speaking about for a number of years now. I recall listening to Dr. Boyd Haley, here in Toronto about 5-6 years ago, outlining the the problems with mercury and the effects that various forms of mercury can have on the body. I am happy to see that this recent study was done here in Toronto, and am interested in following up on it.

Doug Troutman

Well...this is EXCELLENT information that reiterates the toxicity of mercury and it's correlation to testosterone. This is how science works, by building a consortium of information from different fields of study, and coming up with the same conclusion. This can lead to the advancement of treatments to this mercury induced disease.


Hey Deb,

Do you know offhand the chapter or page in which DK talks about this issue in EoH? I read the book (I admit I do not have a photographic memory), but do not remember this information. I'm hoping you know the general location?



I don't mean to be disrespectful but this is not NEW information. This info has been known (by me at any rate) for about 3 maybe 4 years now. I think David Kirby even made mention of this issue in EoH.

Again maybe it's just me but this is not news or even note worthy at this late date.


For once estrogen is a good thing.
Not to over simplify but my youngest a girl had very toxic Mercury levels but avoided Autism. My 2 boys are faring the worst from shots, one with full blown Autism one very ADHD. My oldest daughter who was unfortunate enough to have an amalgam at 18 months recovered quickly from severe learning disabilities with a year of chelation.
A DAN practitioner once said to me...give me a girl and I'll get em' recovered.
This is a very sad battle of the sexes.
One that could be very easily avoided.


I just read an article today that Sara Palins sisters son has autism!!!!!!!

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