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  Whenever I talk to practitioners about thyroid health, like I recently did at MINDD, I can guarantee I’m going to get 2 questions:

  1. Shouldn’t we aim for the high iodine intake of Japanese?
  2. Can we use the patch test for testing iodine levels in our patients?

I am so glad you asked.  The answers are no and no.

I am a nutter for minerals and iodine just won’t go away right now.  Too little = a problem, too much = often the same problems. To boot we are faced with radically contrasting views on assessment and dosage and just about everything iodine related. It’s not you – it’s iodine.  Trust me it’s a complex little mineral that requires some extra thought and caution.  If you imagine the Japanese have no thyroid problems – correct that big myth right now by reading this scientific paper that refers to health problems that result from too much dietary iodine.  It also explains that the typical first step in treating hypothyroidism in Japan is to reduce their iodine intake!

But more importantly, let’s talk about assessment.

I wish the patch test worked. What a fabulous cheap in-house assessment tool this would be and I am all for more of those…but the bad news is, it doesn’t.  Painting a ‘patch’ of betadine or other iodine solution on your skin and then waiting to see if the colour is gone by morning tells us nothing about the true iodine status of the patient.  The disappearance of the colour results from a) evaporation off your skin estimated to constitute approx 88% of total iodine and b) iodine converting to iodide – this reaction happens readily.  The rate at which the colour disappears relates therefore to things like the temperature and atmospheric pressure of the room and also the hydration of your skin…not your need for iodine. 

Have no doubt, you do absorb iodine that is applied to your skin.  There are oodles of published case reports that show dramatic changes in thyroid function (both hyper & hypothyroidism) in individuals following being ‘painted with betadine’ as an antiseptic post burns or surgery. Good to know there can be dermal uptake but it is not a preferred or reliable way to address iodine deficiency because we can’t always be sure of the dose we’re administering via this route nor the magnitude of this effect.  So go back to oral dosing where you can control the dose and you know the uptake and distribution kinetics.

Sorry, but I am glad we’ve had this conversation.

And remember if you have a question – other people will have it as well…so keep asking them :)

The iodine landscape has undergone radical change recently.  We’ve moved from recognising the resurfacing of a widespread deficiency, to large-scale food fortification that has failed to correct deficiency in most and produced excesses in a few. Parallel to this, we have the ever growing incidence of thyroid disorders and some radically contrasting ideas regarding iodine‘s role in both aetiology and treatment. Micrograms V milligrams?  Random urinary iodine or iodine loading test? Important new evidence and clinical experience helps us understand more about how to accurately assess patients’ need for iodine and know when & how to use it therapeutically & when not to!  

Rachel has just released an epic 3 hr update on everything you need to know about iodine, an extended remixed version (!!) of a very well received presentation on this topic for AIMA NZ last month.  If you are looking at iodine or thyroid health in patients – this update is a must.