You're right; iodine deficiency is rare in the U.S., though there are some areas that are prone to it. Enlarged thyroid can be caused by inflammation of the thyroid, as a result of autoimmune disease, such as Hashimoto's or Graves Disease.
Hashimoto's is most commonly characterized by hypothyroidism, but in the early stages, it's not uncommon to see swings of hyper, as well. Graves Disease is predominantly hyper, though eventually, those patients become hypo as well, whether it be from the autoimmune disease, thyroid removal, RAI, etc.
With an autoimmune disease, the body sees the thyroid as foreign and produces antibodies to destroy it. As the destruction process progresses, the thyroid makes less and less of the T3 and T4 hormones, until eventually it doesn't make any.
You need to get tested for thyroid antibodies, Thyroid Peroxidase Antibodies (TPOab) and Thyroglobulin Antibodies (TGab) to test for Hashimoto's and Thyroid Stimulating Immunoglobulin (TSI), which is the definitive test for Graves.
You also need to be tested for the Free T3 and Free T4, which are the hormones actually used by the body (not the same as total T3 or total T4). TSH is a pituitary hormone and should never be used, alone, to diagnose or treat a thyroid condition.
You should also get a thyroid ultra sound, as that will confirm/rule out nodules on your thyroid, which could possibly leak hormones, independently of the thyroid, though many of us have nodules, and they are of no concern.
Thanks for the reply. I don't think it's iodine deficiency as I grew up in the US and it's rather rare here. I plan on visiting another endo and inquiring to see if its ok to ignore this as I was told to do. My debilitating symptoms make that difficult however. I couldn't find any other reasons for thyroid enlargement other than thyroid disease or iodine deficiency online. I wonder if there are non-thyroid related diseases that can cause this, hmmm...Anyway, thanks for the well wishes. My fingers are crossed that this doc can help me out!
Thyroid can enlarge for many reasons, but commonly iodine deficiency. How the thyroid works is a mystery, even to top professionals in the medical field, lab results are used to diagnose thyroid disorder, then treatment applied. Work closely with doctor or Endo, and your thyroid will be takin care of.
As for why? we all ask this question daily. My thyroid swelled 4 yrs ago, and even now, no one knows why? What's important is proper diagnoses/treatment to better health. Wishing you well. Good luck !