I have had the TSH, T3 and T4 and Frees for years and they still never came up. And the last several years I was definitely experiencing Thyroid symptoms (although I did not know then) and then... one day I believe it was the T3 numbers that blew. The test had been normal 6 months prior. The symptoms I was having was extremely dry skin and hair, my hair growing like nuts, and joint pain in the knees.
I just thought my skin was dry from moving to the SW, my hair crazier than ever because I am almost all grey now and knee joint pain just from the progression of Fibro and ME/CFS so I never mentioned these things to my doctor (except the knee joint pain) and if I had been a normally healthy person who all of the sudden developed dry hair and skin I may have mentioned it to my doctor but being so sick with so many symptoms I only have the wherewithall to go over the plethora of information I know are illness related.
It was so far off that my Primary thought it was a lab error and my Rheumotologist office already wrote the script for me to have the follow up. It was still showing bad numbers. I went on meds and 2 months later the numbers returned to normal.
So for me, the continuous neuro-immune fight and overall body fight I have had with Fibro and ME/CFS for 40 and 35 years may have finally made my thyroid blow. I feel 5-10% better now on medication but I am still greatly disabled. And that is only 5-10% better after my body took a dip in the way I felt the last few years.
Here is the thing. You can have full thyroid panels like I had with normal ranges and your thyroid could still be blowing because the pituitary gland kicks in and makes up for what your thyroid is not doing. It can't do that forever but it can do it for a few years.