Hello Rhwittman:
Well, back when I was diagnosed in 1987, I was put on Levo and I took it but my TSH never would come down. When I was 12, I noticed I was constipated a lot, I hated cold weather and felt cold inside my body. When I was in my 20's and in college for Nursing, my professor said you have a Goiter. I was not heavy and was normal sized. I was diagnosed a bit later and I could not understand why my TSH was not coming down into normal range.
You feel like some kind of criminal as I explained to my doctor, I was taking my Levo. So he switched me to Thyrolar a combo of T3 & T4 and still no big change.
I went onto Armour Thyroid aslo called NDT, and things got better. However not great and my TSH was still on the higher end. So it was finally figured out, I can't convert T4 into T3.
Now you are not as bad as I because your blood work is good except for the TSH. The antibodies if not treated will damage the gland so if you are on replacement hormone you give the thyroid extra help and that is good and keeps your body from getting a goiter and from more damage.
I did gain some weight but I am now on T3 Liothyronine only and I lost over 32 pounds and you should watch carbs. I do walking 1/2 hour a day -you can do a little at first and then progress up to 1/2 hr. I also swim.
As to your question about a slow thyroid, it may be damaged by the Antibodies and it made it not work as well. Your thyroid is making horomones but your sensor TSH is not normal and it is an early sign like a call for help!
I think you are at an early stage of the autoimmune disease and some people swing between Hyper too much and then go later into a more Hypo state. It is a slow process and it is good news your T3 and T4 are okay.
Side effects can happen, I experienced loose bowels. Not now but early on. I feel more alive now, on just T3. I used to sleep a lot in the early days in my 20's. Too bad we can't get that time back.
Yes, see an Endo as it may be helpful as that is all about the thyroid and they can tell you more. Both your GP and Endo need to see you.
I hope this helps, ask any questions you have.
Shelly