Hyperthyroidism Support Group
Hyperthyroidism (or "overactive thyroid gland") is the clinical syndrome featuring weight loss (often accompanied by a ravenous appetite), fatigue, weakness, hyperactivity, irritability, apathy, depression, polyuria, and sweating. Additional symptoms may include palpitations and arrhythmias (notably atrial fibrillation), dyspnea, loss of libido, nausea, vomiting, and...
I am not sure where you are at with the FT4 and T3 ranges, but these should be in the middle at least.
RAIU doesn't determine if one has Graves' Disease. It is useful only if there are thyroid nodules involved.
As for the AFIB, I try to make sure not to have issues with this and often times the triggers are from either in the diet that I was exposed to let's say GMO, chemicals and toxins as well as household and personal products used that set me off. Even smelling something (as I have multiple chemical sensitivities) can cause me to react.
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I do what I can to lower down the thyroid antibodies. So that for me is diet, environmental, the products I use around the house and on me.
I cannot remember if you tested for any thyroid antibodies? If you had were any of them positive?
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For you I'd find out about the TSI and the TRAb for GD and see what's going on Hashimoto's with TPOab and TgAb. If getting these has been awhile for you?