Question normal

1) What is your approach in a patient presenting to the hospital in AF with RVR who does not have any known h/o thyroid disease and TFTs reveal normal TSH but elevated T4. No underlying infection.
2) What if you encountered a similar scenario in a patient who is on Methimazole for hyperthyroidism?
3) Similar scenario but this time the patient has h/o hypothyroidism and is taking Synthroid?

I appreciate your help. This has been a challenging topic for me.