<s>[INST] I have had hypothyroidism since age 5.  My doctor told me when I was in my 30s that when I get older my thyroid condition would cause complications.  Ive also been told I have a slow heart rate.  When I ask my current doctor what causes my chest to frequently feel so weak and tired, she has no idea what Im talking about. [/INST] Thanks for your question on Chat Doctor. I can understand your concern. In my opinion, we should first rule out heart related diseases for your symptoms because you are having hypothyroidism and slow heart rate. So heart blocks can cause similar kind of symptoms. So consult cardiologist and get done ECG, 2d echo, stress test (trade mill test) and Holder monitoring (24 hours continuous recording of ECG). If all these are normal then no need to worry about heart block or other heart diseases. Sometimes uncontrolled hypothyroidism can also cause similar symptoms. So get done serum TSH and free T3, free T4. If it is altered then you should change your thyroid Chat Doctor. So consult doctor and discuss all these. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks. </s>