For the past year I've been getting more and more breathless. I ended up in hospital with suspected heart failure, but the cardiologist said my heart wasn't too bad for my age of 74 years. Waiting for pulmonary tests and to see a neurologist. I am on 20mcu T3 and 125mcu T4 . Same dose for over 10 years. My blood tests are normal, in fact my TSH is suppressed because I take T3, so no increase in medication. I have today told my doctor I shall not take the T3 for a week and take an extra 50mcu T4 instead, then have a blood test and see what my TSH is. I have night oxygen as I kept waking up, sometimes, with adrenalin rushes other times with a strange feeling as if I was going to pass out. I am so breathless I can't speak on the phone. My doctor has now prescribed mobile oxygen. I am getting desperate as the air hunger is at a serious level. I was diagnosed with mild sleep apnea and use a CPAP machine at night with the oxygen. I seemed to have got more breathless since using the CPAP machine. Rang the hospital and they said machine should not make me breathless. I wondered if the carbon dioxide was building up in my blood from the CPAP machine? I have muscle weakness in my shoulders in that I can no longer raise my arms above my head in fact I can barely move them. Please, please can anyone tell me if they have had a similar problem or could it be my thyroid? Thank you so much.