I am 55, female and have had an under-active thyroid since my 1st child was born 38 years ago. Since then I have been on thyroid hormone (mostly synthetic). I was doing fairly well, but in 2000 my doctor said he thought I would feel a lot better on natural hormone instead of Synthroid, so we changed my pills. I started to get chest pains. They would come in waves. Dr. tried to switch me back to the Synthroid, but I still got really bad chest pains. He tried every other kind of thyroid on the market and they all gave me chest pains. He thinks it may have happened because I was also taking Tamoxifen at the time after a lumpectomy & radiation for breast cancer, since it also has an effect on the hormones. (I have been cancer free since 1997) We stopped all thyroid, and then I started getting severe chest pains on antibiotics for sinus infections. I finally stopped the Tamoxifen after 4 years instead of 5 to see if that would help. I still get chest pains on certain antibiotics (thankfully I found a few I can still take!) but still can not get back on thyroid hormone. I am so tired now, after 7 years, I am almost bed-ridden! I can hardly get my breath when I walk, my legs feel like lead weights & I cannot stand for long. Doctors look at me like they have never heard of this, like I'm the only person in the world that has ever had this happen. I am desperate!!! Does anyone have any idea what's happening to me??? Thank you so much for any help you can give me. If I don't soon get back on thyroid I'm afraid I will never get out of bed!