I have a partially empty sella and I have been suffering from brain fog, allergies to everything (according to tests) including foods, and have low adrenals, low normal testosterone, mid range normal T3, and low normal T4. I think the brain fog could be allergies related and the doctors tell me the allergies are because of the low levels of the three hormones. On the other hand the brain fog could be from low hormone levels.
My doctor is adamant that increasing my levothyroxine to raise my T4 level will not make me feel any better. She raised my testosterone meds and I do have a little more energy but the brain fog and allergies live on.
All of my thyroid levels are normal except T4 with it being on the low end. I have severe hypothyroid symptoms-temp 96.7 every morning consistently, freezing cold, losing eyebrows, etc. My testosterone is also fairly low for my age and body type(natural bodybuilder) at 405. I have brainfog so bad that I can barely function. No allergies or other health concerns. T4 is still within range so they will not treat it. Hopefully your doc will give it a chance! Good luck! Wish you the best!
I think the low T4 is most likely the culprit, but low cortisol can do that too. Are you on any adrenal hormone replacement? I disagree with your Dr about the T4. It seems a tiny bump up in the dose to get your T4 in the upper part of the range would be helpful.