What Causes Dizziness, Lightheadedness, Fatigue And Memory Loss?
Anxiety a possible contributor.
Detailed Answer:
I read your question carefully and I understand your concern.
The fact that you've had a CT and MRI is very reassuring, it means that serious issues like tumor have been excluded. At your age degenerative brain conditions are also highly unlikely, the normal MRI reinforces that as usually there are some changes on imaging as well.
Thyroid conditions or vitamin B12 deficiency could potentially cause such issues but given the tests you have provided the results do not justify the symptoms, that antibody count alone is not enough if the rest of the thyroid function findings is normal. What could be further explored regarding hormonal alterations be cortisol levels which I suggest to be checked to rule out adrenal gland insufficiency.
Hemoglobin level may also be repeated in order to check for conditions like polycythemia vera, but I don't think it will be the case, your values are almost normal, do not justify the symptoms and are much more likely to be due to not drinking enough water.
If the cortisol tests come out normal as well, given the normal results in other tests, I would say that the most likely cause would be a psychological cause like anxiety and depression. Anxiety can manifest with those symptoms and looking at past questions of yours I see you have had anxiety issues in the past which mean you are prone to it. So I would discuss with your doctor the possibility of starting regular treatment, not with benzodiazepines as you have done in the past (which are not to be taken for long as they create dependence and tolerance) but with an antidepressant which are first choice treatment for chronic anxiety issues.
I remain at your disposal for other questions.