Northern, yes lithium will effect thyroid.......been there!! Lithium molecules and iodine molecules(essential for thyroid health) are similar in shape, weight and atomic activity. The thyroid gets confused and sucks both molecules up. The lithium and iodine fight for first chair and the thyroid suffers.

A very simplistic explanation......I was on thyroxine and lithium and made me thyrotoxic(at that end of the scale anyway with TSH). I was dx bipolar II but not so sure now. Sodium valproate and carbamazapine(I think) are not goiterogenic.

Sorry to say this, but your doctor is an idiot( I am a little counter productive today, sorry) and you need to see a proper psychiatrist.

Good luck babe.......