Thyroid and the environment: exposure to excessive nutritional iodine increases the prevalence of thyroid disorders in São Paulo, Brazil

[helvella]

We have had many discussions about iodine - specifically, iodine supplementation.

This paper from 2008, which I do not remember ever seeing, is quite interesting and is fully accessible.

Thyroid and the environment: exposure to excessive nutritional iodine increases the prevalence of thyroid disorders in São Paulo, Brazil

in European Journal of Endocrinology

Authors:Rosalinda Y A Camargo, Eduardo K Tomimori, Solange C Neves, Ileana G S Rubio, Ana Luiza Galrão, Meyer Knobel, and Geraldo Medeiros-Neto

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(Correspondence should be addressed to G Medeiros-Neto; Email: [e-mail])

DOI: doi.org/10.1530/EJE-08-0192

Volume/Issue: Volume 159: Issue 3

Page Range: 293–299

Article Type: Research Article

Online Publication Date: Sep 2008

Abstract

Objective

To evaluate the prevalence of chronic autoimmune thyroiditis (CAT) and iodine-induced hypothyroidism, hyperthyroidism (overt and subclinical), and goiter in a population exposed to excessive iodine intake for 5 years (table salt iodine concentrations: 40–100 mg/kg salt).

Design

This was a population-based, cross-sectional study with 1085 participants randomly selected from a metropolitan area in São Paulo, Brazil, and conducted during the first semester of 2004.

Methods

Thyroid ultrasound examination was performed in all participants and samples of urine and blood were collected from each subject. Serum levels of thyroid-stimulating hormone, free thyroxine, and anti-thyroid peroxidase (TPO) antibodies, urinary iodine concentration, thyroid volume, and thyroid echogenicity were evaluated. We also analyzed table salt iodine concentrations.

Results

At the time the study was conducted, table salt iodine concentrations were within the new official limits (20–60 mg/kg salt). Nevertheless, in 45.6% of the participants, urinary iodine excretion was excessive (above 300 μg/l) and, in 14.1%, it was higher than 400 μg/l. The prevalence of CAT (including atrophic thyroiditis) was 16.9% (183/1085), women were more affected than men (21.5 vs 9.1% respectively, P=0.02). Hypothyroidism was detected in 8.0% (87/1085) of the population with CAT. Hyperthyroidism was diagnosed in 3.3% of the individuals (36/1085) and goiter was identified in 3.1% (34/1085).

Conclusions

Five years of excessive iodine intake by the Brazilian population may have increased the prevalence of CAT and hypothyroidism in subjects genetically predisposed to thyroid autoimmune diseases. Appropriate screening for early detection of thyroid dysfunction may be considered during excessive nutritional iodine intake.

Full paper freely accessible here:

eje.bioscientifica.com/view...

[greygoose]

Well, surprise surprise!

[Alanna012]

I remain completely confused on the subject. Personally any iodine intake and my thyroid feels like it's on fire the next day, and I feel very crumby....but I have had two private doctors specialising in thyroid tell me I still ought to supplement and indeed recommend iodine itself (as kelp) or iodine containing formulas.

On the one hand some say avoid, on the other hand there's a thought by some nutritional gurus that NO ONE is getting enough iodine in the industrialised western diet.

On forums I have exchanged messages with people who are all but bathing in lugols....happily. In others, people who avoid it and have a low iodine diet and feel better.

Some say this is part of the benefit of the Mediterranean diet, iodine being a by product of a diet that includes more fish,

Others that studies in Japanese women eating lots of fish show increased thyroid disorders.

Some, that its fine as long as you take selenium at the same time.

I don't know what or who to believe🤷🏿‍♀️

It irritates my thyroid for certain. So I avoid. But I have read any discomfort is temporary and once you push past the temporary inflammation it gets better, I'm already too ill to bother with the risk!

[helvella in reply to Alanna012]

I think we have to start by suggesting that there is a fundamental difference between individuals who have grown up with barely sufficient iodine and those who have had plenty, possibly an excess.

My view is that people should not be shown iodine supplements as the first step in addressing thyroid issues.

And that, if they do their best to understand and decide they will try some, they should take very modest amounts, at least to begin with.

Yes - the subject of iodine is confusing and much more complex than many think. Including some professionals.

I find it odd that the industrialised western diet is mentioned so often. After all, we see few nowadays with genuine iodine-deficiency goitres.

[Alanna012 in reply to helvella]

Everything you say here makes sense! I don't understand references to the modern diet being sub-par either, but it is often quoted that people took larger doses of iodine in the past. I read a book about iodine in which the author suggested everyone should be taking lugols, rubbing it in and drinking. I tried it and it made my thyroid flare up awfully!

When educated nutritional experts and functional medicine doctors allude to the past it's impossible to know how accurate such summisations are. After all, I never lived that long ago and I haven't the time to compare literature from whatever past they're refering to! It's an easy statement to make.

But I note the same suggestions are made about selenium too. Poor soils, deprived of minerals. It always seems we're not getting adequate amounts of anything that people apparently got plenty of in the past!