I have read that soy is bad for your thyroid in general. I just googled soy's effect on thyroid and there is plenty to read. I remember reading in the past that the surge in soy consumption has been associated with a rise in hypothyroidism and thyroid cancer. I try to avoid soy, but it's hard because it's in virtually EVERYTHING processed. I couldn't believe it when I found out it's in canned tuna!?
BTW, I am so glad that you have figured out why you were so tired. I hope you're feeling GREAT soon!