There are autoimmune diseases that can cause hypothyroidism, too (like Hashimoto's, I think). But even if that's not the cause of your hypothyroidism, have you had your TSH (thyroid function) checked lately? If you were taking too much thyroid hormone (maybe your needs changed), you would have the symptoms of hyperthyroidism.

I'm not saying that's really likely--just worth mentioning to the doctor if you're going anyway. Hyperthyroidism can cause muscle weakness, eye trouble, and anxiety. Two other signs of hyperthyroidism I know of: dirty fingernails (because the nail separates from the bed too soon as it grows, and dirt gets trapped) and hair loss.

Abby