I have not read about a relationship between Iodine and glutamate. However, the possibility explains something I've noticed. I already know from genetic testing that my glutamate receptors have a lot of problems. I put quite a bit of emphasis on keeping them functioning as well as possible and in supporting GABA receptors, as the balance of glutamate and GABA is crucial.
One of the most helpful minerals to support GABA is magnesium. We've mentioned magnesium quite a bit through the years, and this is a clear application for it. As I increase my Iodine dosing, at some point I become overstimulated and have to raise how much magnesium I take. I didn't know why I was overstimulated, just that magnesium stopped it.
I've always had poor RBC Magnesium blood levels, so it becomes critical that my daily magnesium intake keeps up with what gets used up during the day. There's no question that for me more Iodine means more magnesium. Then I feel calm and the iodine gets to do what it needs to do.
If your doctor is willing to test your blood level, a sufficient RBC Magnesium level (NOT serum magnesium) is >= 6.0 mg/dL. But really, a simple experiment is either to add it to your daily supplements, at least twice a day, or increase how much you already take. I've used both magnesium citrate and magnesium malate, while others swear by magnesium glycinate and other forms. Spreading out your intake might help you take more of it before the dread magnesium supersoft stool or diarrhea starts at some point. Then you have to back off the dose a bit.
I like to think this might enable you to get back on the Iodine horse!