I won't call myself an expert and not a doctor, rather based on my own findings and experiences.
Your TSH being in the upper normal range is has strong correlation of Metabolic Syndrome, I'd say your TSH of 3.4 is teetering towards M.S, how is your Triglyceride's/Lipids and fasting Glucose levels?
Are your meals sporadic, go long time between meals, then pig out?
Struggle losing weight?
Inflammation? HS -CRP?
Need to pin point whats causing your rT3 to be elevated, no easy task.
Low serum cortisol and ACTH levels? Do you stress on simple things?
Sub clinical Hypothyroidism,with Sub clinical Hypoadrenia would be my guess …
I don't believe a Pituitary MRI is warranted, but then again I'm not a doctor.
Your rT3 is to high in a ratio of FT3
FT3 3.2/rT3 39X100= 8.2, this needs to be 20 or greater
Did you pull these panels or your physician?
Yes a low dose of T3 12.5 mcgs twice a day would be warranted IMO