Hi Ellen
Maybe your heart pounds quickly and loudly, your hands shake with tremors, you feel dizzy, and it's hard to catch your breath. You break out in a sweat, gripped by a sense of fear. Or maybe you feel your heart skipping beats, racing, fluttering, or pounding. You may not realize that what feels like a panic attack or heart palpitations can be symptoms of hyperthyroidism or autoimmune Graves' disease,Hashimoto’s thyroiditis all of which involve an overactive thyroid. Because your thyroid and your heart are so closely intertwined, having any sort of thyroid disease can result in heart symptoms.
The Link
Your thyroid and your heart are closely linked together and what affects one can affect the other.