Hard to say what happened, but 37.0C in the afternoon is a perfectly normal temp, exactly where you want to be. Neither hypo nor hyper. Levothyroxine only slowly leaves your body. Half of it is gone after 1 week, so you likely have some residual effect from it. Iodine is so necessary to your thyroid; perhaps you were quite deficient and once your thyroid got the Iodine its function came back. Hard to know. But if Iodine is what you needed, and you're not taking it now, it seems your thyroid would slowly go hypo again.