thyroid, goiter,with fairly normal. bloodwork somewhat low TSH

New to site. Hope I post ok.
Have an enlarging thyroid goiter not sure whats the cause, thyroid panel indicated a low TSH and normal T4 values
Going to naturpath who ran a standard food allery test and now is restricting dairy,eggs,wheat, potatoes. corn, oats gluten,tomatoes most grains except millet and brown rice, sugars, basiclly most foods I cant have. I reacted to most veggies, except cabbage, cauliflower, carrots and onions,and garlic.SO its very hard to eat,Meats are allowed.
Dr.Suspects I have leaky gut and this might have caused my thyroid problems.
I basically feel fine except for the growing lump on my neck .
Ultrasound and needle bisopy were negative for cancer 2 yrs ago.
Dont want surgery and wondering if any of you have any advice? Not sure if the diet is helping or not.
The medical doctors thought I was borderline hyperthyroid 6 months ago, but my tests and feelings seem fairly normal now.Should I avoid Iodine or increase it with being boderline hyperthyroid?
Any suggestions?