Re: do you need meds for enlarged thyroid?
TPO antibodies, which are the leading cause of thyroid failure, also can cause chronic hives. You have the classic symptoms of thyroid failure, you know you have low-normal FT4. I'd say that's plenty of evidence that you are hypothyroid.
Endos are notoriously terrible at treating hypoT. They typically specialize in diabetes and haven't bothered to learn anything about thyroid since med school - and most of that information was wrong in the first place. Ditch that dumbo. Sometimes you can do better with an experienced family practice MD or DO. (DO's can be especially good, because they practice holistically.)
You must be tested for TPO and Tg antibodies. That will tell if you have autoimmune thyroiditis (Hashimoto's disease). It could also explain the hives to boot. Also, you need another TSH, free T4 and free T3. The TSH can appear totally normal in cases of Hashi's, but the free Ts will typically be very low normal. If they are, you need supplemental hormone. Period. Finding an MD who understands all this can be hard, but can reward your effort.
If you can get a hold of a copy of Thyroid for Dummies, it will help you understand what you should demand of an MD.
Good luck to you!