It sounds like they are talking about Thyroid Recptor antibodies (TRab).
TRab are antibodies that mimic TSH and attach to the TSH receptors in the thyroid gland. The more TSH receptors they occupy, the fewer receptors are available for TSH to dock at.
That causes the thyroid to slow production of hormones, which causes the body to produce more TSH to tell the thyroid to get busy. But there is less room for the TSH to dock, so the thyroid does not get the message...and it goes on like that.
The doctors can treat your child by running a Free T4 test and a Free T3 test and dose the medication based on the actual hormone tests.
They should be doing that now in conjunction with the TSH test anyway.
TRab is a bit rare, but this is not rocket science for an Endocrinologist. If the doctor is saying they don't know what your child's hormone levels are, but he needs meds regardless, you need to find a better doctor.
The thyroid controls metabolism. It controls a lot of things. It could slow the growth of your son.
Get a second opinion. There is a lot at stake here and if the doctor is hemming and hawing find another one.
can there still be a developmental delay if my sons been taking his synthroid since a week old,his endocrine keeps telling me his delay has nothing to do with his thyroid as long as hes been taking his medication.
also my son always seems to be real confused and not being able to think can this medication do this to him.