I used to use povidone iodine around my belly button to see how long the "stain" would last and that would tell me how my body was doing in keeping iodine in check.  I have been doing this again, as well as taking Nutrafol to regrow my hair AND using iodized salt.  1/4 tsp of iodized salt per day should be enough to do the trick since iodine is a trace element but important to the thyroid.  I never have used a lot of salt on anything but I was using the Himalayan Pink Salt recommended by Dr. Mercola, but now I'm facing a thyroid issue.  My doctor never even said it if was hypo or hyperthyroid, or if it was thyroid storm (dangerous) but now I have to drive to the stupid clinic ONE MORE TIME (this makes 3 times now) for a blood check.  They send the blood to Sioux Falls to be evaluated (how stupid, we have labs all over Rapid City) but by the time it gets to Sioux Falls it's probably degraded anyway.  I may have to seek a 2nd opinion depending on what they tell me tomorrow.  It's supposed to rain cats and dogs tomorrow (lovely) but I don't have my umbrella here or anything (another LOVELY).  So I go in with wet hair, wet shoes and all the rest.  On top of everything else I now have new insurance (I dropped my AETNA and am using Medica for a LOT LOT LOT cheaper and just as good a coverage).  I'm anxious to see how THAT goes, and I told them today when they called to remind me of the apptmnt tomorrow that this is the very last time I'm coming back until that stupid road construction is done.  They have been working on that for over 2 years now.  My agent told me his mother has been using Medica for about 4 years and has never had any issues with it, that's good enough for me.  
The complete list of foods with iodine (mostly fish which i can't stand) is at the link below.

https://www.healthline.com/nutrition/iodine-rich-foods#TOC_TITLE_HDR_24. Iodized Salt"Currently, both iodized and uniodized salt are sold in the United States.The addition of iodine in table salt began in the US in the early 1920s to help decrease the occurrence of goiters, or swelling of the thyroid gland (16).There is approximately 71 mcg of iodine in 1/4 teaspoon of iodized salt, which is 47% of the daily recommended intake. However, salt also contains sodium (6Trusted Source, 17Trusted Source).In the last few decades, iodine intake has decreased in the US. This is likely due to the push of major health organizations to restrict daily sodium intake to prevent or treat high blood pressure.Nevertheless, salt only seems to raise blood pressure in salt-sensitive individuals, which is about 25% of the population (16, 18Trusted Source).

Summary Iodized and uniodized
salt are commonly sold in grocery stores. Consuming 1/2 teaspoon of iodized
salt per day provides enough iodine to prevent a deficiency."

I am usually ALWAYS SHORT on sodium, too.  So the lab lady keeps telling me to eat more salt.  Now I use iodized morton salt, rather than Himalayan Pink Salt.  Mercola missed the mark on this one.  A lot of people are low on both sodium and iodine and don't even know it.  It is often misdiagnosed as heart trouble because of the dizziness involved, sometimes a pounding heart, etc.  You have to know what to look for when you search out information on your own.