It's good to know that the relationship of mood and thyroid is extremely complex, and that bipolar patients are more frequently suffering from thyroid problems, and, that unappropriated thyroid function can give symptoms that are bipolar-like.
It's a rule to get the thyroid gland working properly, before beginning with your treatment for bipolar disorder, because if it's not, you might not respond fully to treatment for bipolar disorder, and when you get your thyroid hormone in the right place, by itself could help your bipolar symptoms somewhat.
Other important thing to know is lithium's ability to interferes with the thyroid system, leading to low levels of thyroid hormones (low thyroid hormones, leads to decreased mood and energy, feeling depressed)
What have happened at the last psychiatrist's appointment?