Especially after exercise, increased fatigue for 2-3 days.
I am doing phys. therapy for back pain. Exhaustion lasts several days.

Thyroid (TSH is in range at 0.65; I don't know what it was before Tx), blood are normal. Docs say that it's not due to Tx, and that it's probably due to stress, depression, etc.though I don't really believe it.

I sleep a lot and am still tired. I used to feel great during and after exercise. Now I feel lousy.

I don't know if the heart and lungs need to be worked regularly and I would get endurance back by pushing thru fatigue or allow myself to rest until I recover somewhat each time.

I have not tried vitamins that some posters mentioned.