Your heart problems could be adrenal fatigue which can be caused from T4 drugs over time, plus many other causes. I took them for so long and pooped out my adrenals. I was very sick. Heart racing, palpitations, panic in the middle of the night...I went to the cardiologist and all tests came back normal. That is what began my research for the answer. If you don't convert T4 to T3, which is common with Hashi's - all that T4 stays in your blood and doesn't get in your cells. You feel "wired tired". It is awful. I would be hyper one day and lethargic the next...I had terrible pain, heat intolerance, dry skin, all the symptoms. Read a little about adrenal fatigue and see if you have symptoms. You need to be sure your adrenals are good before starting T3. I just know that most people do better on a combined hormone treatment. Our thyroid glands produce T4, T3, T2, T1 and calcitonin. If you take synthroid it is a storage hormone. If you can't convert to T3 you will not get rid of your symptoms but your labs may come back normal. I tried the levoxyl and cytomel combo and got very hyper on it. I can't tell you the world of difference I felt on Armour. Endo's don't generally prescribe it. Bad stuff is being said about it by pharmaceutical reps. Synthroid is who sponsors many of the the endocrinology conferences. TSH is the gold standard too. Just know that your doctor may not treat by symptoms and may not use Armour. If you don't begin to feel better just know there are options. I suffered for 15 LONG years and would love to help someone avoid that...I have told my brother all of this and he continues to feel bad and not try something different(TSH=96, antibodies=924). It takes a lot of work to get what you need. You have to be willing to change doctors until you find one that will help. Audrey is right that doctors have to be careful. The gold standard is to keep TSH in range. The medical board could come down on doctor for prescribing meds to someone subclinical (TSH normal but all the symptoms). This way of treating is how it needs to be but not taught that way in school. Sometimes calling a compounding pharmacist can be helpful to get a recommendation of a good hormone doctor. This has helped me get what I need. I have 7-8 books on thyroid, adrenals, iodine. Knowledge is power. Keep reading and asking questions and you will get there. You can feel much better!!!
Audrey, I agree with everything you say...we seem to be reading the same information and are getting what we need. I feel bad for all the sufferers out there. I am a physical therapist and see many patients, especially elderly, struggling with low thyroid symptoms despite being on meds. The TSH standard is not working!!