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Effect of iodine restriction on thyroid function in subclinical hypothyroid patients in an iodine-replete area

I told you that iodine is controversial. :-)

Thyroid. 2014 Jun 3. [Epub ahead of print]

Effect of iodine restriction on thyroid function in subclinical hypothyroid patients in an iodine-replete area: A long period observation in a large-scaled cohort.

Joung JY1, Cho YY, Park SM, Kim TH, Kim NK, Sohn SY, Kim SW, Chung JH.

Author information

Samsung Medical Center, Sungkyunkwan University School of Medicine, Division of Endocrinology & Metabolism, Department of Medicine, Thyroid Center, Seoul, Korea, Republic of ; jiyoung.joung@samsung.com.



Excessive iodine intake is related to a higher prevalence of hypothyroidism, including subclinical hypothyroidism (SCH), in iodine-replete areas. This study aimed to evaluate the effect of iodine restriction on thyroid function in SCH patients in an iodine-replete area and analyze the relationship between serum thyroid stimulating hormone (TSH) levels and iodine intake.

Subjects & Methods

The study consisted of 146 consecutive patients who were diagnosed with SCH at the Samsung Medical Center between 2010 and 2012. Urinary iodine concentration (UIC) was measured in 82 patients; of these, 20 patients with UIC <300 µg/L were excluded, and 62 patients with UIC ≥300 µg/L were educated about the restriction of iodine-rich foods. Following the first follow-up visit, these patients were divided into 2 groups based on the UIC level: group A (well controlled iodine intake, UIC <300 µg/L, n=40) and group B (poorly controlled iodine intake, UIC ≥300 µg/L, n=22). The remaining 64 patients did not restrict iodine rich foods (group C). The 82 patients with measured UICs were reevaluated every 3-6 months, and the median follow-up was 13 months (range 3-32 months). Thyroid function and UIC were measured at each visit. The correlation between serum TSH level and UIC was determined for the 82 patients in whom UIC was measured.


Following 3-6 months of iodine restriction, the serum TSH levels significantly decreased in group A (9.0 mU/L to 4.7 mU/L, p <0.01). In addition, the serum free T4 levels in group A significantly increased (1.11 ± 0.23 ng/dL to 1.18 ± 0.17 ng/dL, p <0.05). However, there were no significant changes in serum TSH or free T4 levels in group B and C. Serum TSH levels were significantly correlated with UIC (r=0.33, p <0.01).


Iodine restriction may normalize or, at the very least, decrease serum TSH levels in SCH patients, and serum TSH levels are strongly correlated with UIC. Therefore, restriction of iodine intake could be a primary treatment option in SCH patients in an iodine-replete area.




Full paper is not available to us mortals. :-(


Image: By Jurii. Lanthanum-138 at en.wikipedia [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

18 Replies

And here I was thinking iodine was bright yellow :-D

So, if subclinical hypothyroid patients adopt a low iodine diet they may reverse or improve their hypothyroidism?

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Iodine dissolved in alcohol gives us the intense yellow - even when the alcohol evaporates you get the yellow form. As crystals it is deep purple. But in this form it looks metallic, doesn't it? This photo seems to show these same metallic crystals giving off a purple haze.


That is what it seems to say - but surely far too simple! I find everything to do with iodine so confusing. That we have some people saying 150 micrograms is enough. Some say that the Japanese who might consume up to 3000 micrograms are the highest iodine consumers in the world. And others that it might be necessary to take 45000 micrograms.

Many suggest that having enough selenium at the same time is also a critical aspect.



I wonder how quickly one feels any effects from consuming iodine. I had several holidays where I mostly consumed freshly caught fish, lobster and prawns and I felt wonderful.

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How could you, as the single subject of the experiment, make any judgement as to whether it was the iodine content, the proteins, the salt, ..., or the chips? :-)

Still interesting to speculate.

I am always saying that iodine needs to be researched and thought about - and it should not be something to grab while at the supermarket because, well, it sounds as if it might help.



Thinking on it, it was probably the rum :-D


I had a blip the other week after seafood/samphire

actually I seem to remember it before in France after 'fruit de la mer'

drat & double drat :(



Purple Haze, wasn't that Jimi Hendrix? Who knew he was writing about iodine. PR


Ha its the ring tone on my mobile(purple rain)

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wasn't that Prince or the symbol? but hey it's purple & weather related J :D


Yes was prince I will giggle now thinking of iodine every time my phone rings x


I tend to think it's yellow - like mustard (also in Dijon)


Maybe I could change it to we all live in a yellos submarine, dont know how many of us is old enough to remember that lol


I'm old enough to wear the Beatles badges under my tunic lapel (I went to a posh school for 'ladies' Dad was annoyed at the obvious waste of money lol!...)

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That's Prince, before he became The Artist Formerly Known As :-D


he probably didn't either :D


I can never make up my mind whether Purple Haze or All Along The Watch Tower are my fave Hendrix tracks.


Well, Leonard Cohen knew that he was writing about iodine:


I needed you, I knew I was in danger

of losing what I used to think was mine

You let me love you till I was a failure,

You let me love you till I was a failure --

Your beauty on my bruise like iodine

I asked you if a man could be forgiven

And though I failed at love, was this a crime?

You said, Don't worry, don't worry, darling

You said, Don't worry, don't you worry, darling

There are many ways a man can serve his time

You covered up that place I could not master

It wasn't dark enough to shut my eyes

So I was with you, O sweet compassion

Yes I was with you, O sweet compassion

Compassion with the sting of iodine

Your saintly kisses reeked of iodine

Your fragrance with a fume of iodine

And pity in the room like iodine

Your sister fingers burned like iodine

And all my wanton lust was iodine

My masquerade of trust was iodine

And everywhere the flare of iodine


There are some studies that suggest that iodine must be balanced by sufficient selenium.


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