Anyone able to tell me what the symptoms of an underactive thyroid are? I've long been wondering if anything is up with mine! Whenever I'm not carefully watching what I eat, the weight creeps on quite quickly, and it seems to take me a month to lose a pound. (5x a week exercizing, too!) I used to be heavier, but when I lost the weight, I was much younger. Wondering if a thyroid thing has crept up on me, seeing as I'm much more active than I was before. I've been diligently trying to take off the weight I put on last fall, and I feel like it is all happening in super slow motion.