Brief Answer:
Prolactin
Detailed Answer:
The picture is a bit unusual here. When a given individual has positive TPO it is likely they have Hashimotos which typically results in an under active
thyroid. This manifests as a low or normal T4 with higher than normal
TSH. Your TSH is also on the low normal side. So it does not fit the classic picture of a severely under actice thyroid that causes a significantly elevated TRH and TSH, of which the the TRH from the
hypothalamus promotes a rise in the prolactin. In this well described circumstance, treating the underactive with
thyroxine, and normalizing free T4 and TSH often lowers the prolactin back into normal range.
In your situation, this explanation cannot be applied. You need a thorough work up for your prolacitn as well. I have noted the normal MRIs. It is good that apparently there is no
tumor.
Are you on any medications?
Are your menstrual cycles normal?
Have you had labs for
CBC
CMP
Total T4
Total T3
T3 resin uptake
beta hCG
I would even consider an 8 am serum
cortisol level along with IGF1
This requires a systematic evaluation by an
endocrinologist. I understand you are seeing one but perhaps a
second opinion for an in person assessment wont hurt