i dont recommend tests unless you absolutely have to know whats happening or you have some specific problem/question which is rare. bottom line on Iodine is its essential, its daily and 100mg or more a day is needed for full benefit. if it takes 3 months or three years to reach sufficiency it doesnt change what you should do the rest of your life.
just automatically make sure you have enough oxygen, water salt and iodine. make those a surety and a habit and use youre intellectual powers for other things beyond those. thats because nothing else will work right or as well without those basics.