Thank you Midwest,
We will go this week to the endo so I'm trying to read and ask as much as possible to know what to ask and what to look for. I read about how ranges were changed...was as high as 39 and 20 in some guidelines.
Now endos want to lower them again for safety and maybe to get more work

joke.
If I had to guess, the FT4 was barely within their lab /hospital's range within a few decimals but obviously you want to be somewhere in the middle. I also read about sub-clinical hypot and problems it can cause later in life. Maybe that's what the pediatrician meant. All we know was the accepted threshold for one (TSH most likely) was 4 but she tested a 7 and then 1 was the accepted number for (T4 something, I remember from scanning the prescription) and the baby had a 1.000x or so. Either way the T4 was barely normal.
We'll start the meds, better safe than sorry and was relived to learn that meds can make even extreme cases almost go away.