SSRI toxicity on thyroid ?

[Emmanuelle33]

I've read that SSRIs contain halogen atoms that can substitute for Iodine (itself an halogen), making thyroid hormones inefficient.

Will it show on the biology (normal T3 and T4 and higher TSH because it will not slow TSH secretion) ?

I can't find anything online...

[Lalatoot]

it is estimated that 90 percent of the body's serotonin is made in the digestive tract. Something that affects serotonin alters gut function which in turn can affect the absorption of ingested thyroid hormones. Some folks on levo need a slightly higher dose when on SSRIs to compensate.

I was on an ssri for years due to be undermedicated. My tsh was not abnormally high for my in range ft4 result. Usually around tsh 4 {0.27 ~ 4.5} ft4 15 {10 ~ 25}.

[Emmanuelle33 in reply to Lalatoot]

Thank you Lalatoot. Hypothyroidism and gut malabsorption is a bit like the question of egg and chicken... SSRI do inhibit the recapture of serotonin in the synapse. Does it do so in the digestive system ? I do not know...

[Lalatoot in reply to Emmanuelle33]

Yes it does. It is documented. I can't cite the documentation at the mo but will look later.

[Lalatoot in reply to Emmanuelle33]

Serotonin and SSRIs like Prozac can have a major effect on gut bacteria. When exposed to serotonin, specific gut bacteria grew to higher levels. However, when exposed to SSRIs, the bacterium grew to much lower levels in mouse models.neurosciencenews.com/ssri-s...

There are plenty more research papers with similar results if you do a google search.

[helvella Administrator]

It seems to me important to recognise that not all SSRIs contain any fluorine at all. Though the majority do.

Sertraline, dapoxetine and vortioxetine do not.

There is also the slight confusion about closely related medicines. I found a picture which shows many SSRIs and related substances and specifically identifies those which contain fluorine - look for green "F"! (The green is not as strong a colour as it might be.)

upload.wikimedia.org/wikipe...

I have been unable quickly to find clear pathways which show what can happen to the fluorine atoms.

[Emmanuelle33 in reply to helvella]

Thank you so much Helvella. That is very useful. Is fluorine the only halogen found in antidepressant ? I see Chlorine on some of them.And yes, the question is what happens to them ? Do they become free from the molecule and can then be mistaken with iodine ?

[helvella Administrator in reply to Emmanuelle33]

No - as you say, some contain chlorine. But as the rest of the time we see lots of people saying we need to consume plenty of salt (sodium chloride), I find it difficult to get wound up about a few chlorine atoms!

Though I am well aware that there are nasty chlorine compounds ranging from pure chlorine gas through phosgene.

We need to look very carefully at precisely what happens in order to establish the issues and risks. And I have not yet found sufficient detail.

[helvella Administrator]

It is so very easy to see that many contain fluorine, and assume that is involved as the mechanism by which an SSRI might affect thyroid hormones.

But fluorine covalently bound in an organic compounds is so very different to fluorine in an ionic state (e.g. sodium or calcium fluoride).

[Emmanuelle33 in reply to helvella]

Thank you so much Helvella !I’ll keep on prescribing Prozac !

It rarely induce weight gain...

[Emmanuelle33]

Thank you Scrumbler, it’s very interesting !