Hi Gramma,
A TSI test is used to confirm Graves' disease. Now that FT4 is low, if you had TSI, it would probably be falling now. If you had high levels of other thyroid antibodies such as thyroglobulin and TPO antibodies show up during your diagnostic workup, these two could be used to help confirm Graves' disease.
Even though an FT4 of 1.0 is within range, for most people it would be too low for the body's needs and could cause symptoms of hypothyroidism. Your elevated TSH suggests that this is the case. Depression is one of the earliest symptoms of hypothyroidism to occur. Other symptoms include joint pain, weight gain, etc. Similar to hyperthyroidism, hypothyroidism usually causes a few predominant symptoms but not all symptoms.
If your next labs still show a low FT4 it's likely that you've moved into subclinical or overt hypothyroidism and may want to ask about thyroid replacement hormone. Both thyroiditis and Graves' disease can move into spontaneous hypothyroidism. Best, Elaine