Well there are two things that can cause mental impairment:
Hashimoto's encephalopathy: This is where your antibodies attack the brain milan and literally cause degradation of mental pathways. Determining you have it is a pain. Lumbar puncture and lots of neurological tests ruling out all other sources of mental deteriation.. etc. There was a recent study that one women who was determined to have HE and treated successfully didn't regain her mental function until after a total thyroidectomy. Just one more reason why I am going to push for a TT.
Hashimoto's Encephalopathy is documented to be underdiagnosed, in many cases it is passed off as early maternal dementia in conjunction with hypothroidism.. or many other neurological disorders, such as stroke, Alzheimers, psychosis, Wilson's Disease, Pick's Disease, brain cancer, primary progressive aphasia. So given our knowledge of how hard it is to get just hypothyroidism imagine getting an MD to not blow you off until you couldn't fight for yourself. I started my road to diagnosing me for HE back in July.. I am still working toward it near a year later. You can treat it, but currently it is believed to not be curable. Long term prognosis for those caught early on in the disease is good with proper treatment. It is also a relapsing condition, and a steroid responsive disorder, treatable with oral corticosteroids (Prednisone or its derivatives.)
So what are the symptoms? Hashimoto's Encephalopathy typically accompanies high antithyroid antibody titers >1000. If you are not consider to have Hashimoto's Thyroiditis at the time of detection you will eventually be diagnosed with Hashimoto's Thyroiditis as well. Just takes time to find the right MD. *snort* As with any disorder you may have one or more of the symptoms initially, and the farther into a disease the more symptoms and higher degree to the symptoms. So look at these:
* Concentration Problems
* Attention Span Problems
* Difficulty Retaining Information
* Short Term Memory Problems
* Seizure Activity
* Monoclonal Jerks - Involuntary Muscle Jerks
* Coordination Difficulties
* Episodes of Stroke
* Episodes of Stroke-Like Deterioration
* Right Sided Hemiparesis - Right Sided Partial Paralysis
* Aphasia - Speech Difficulties
* Articulation Difficulties
* Word Finding Difficulties
* Fine Motor Movement Problems - Coordination of arms, hands, fingers.
Fun huh? Here is the article on a cure:
Thyrotoxic autoimmune encephalopathy in a female patient: Only partial response to typical immunosuppressant treatment and remission after thyroidectomy .
Clinical Neurology and Neurosurgery , Volume 109 , Issue 5 , Pages 458 - 462
N . Yuceyar , M . Karadeniz , M . Erdogan , A . Copur , A . Akgun , E . Kumral , G . Ozgen
Now after scaring you with the nastiness of Hashimoto's Encephalopathy and what I have gone through.
How can just plain hypothyroidism cause cognitive impairment?
Here is a good article if you can get it..
Is cognitive impairment related to hypothyroidism improved by hormone-replacement therapy?
Authors: Capet C.; Jego A.; Denis P.; Noel D.; Clerc I.; Cornier A.C.; Lefebvre H.; Levesque H.; Chassagne P.; Bercoff E.; Doucet J.
Source: La Revue de Medecine Interne, Volume 21, Number 8, August 2000 , pp. 672-678(7)
In a fetus low T4 in the first twelve weeks is known to increase the chance of neurological cretinism. Something similar is suspect to occur in women with too low T4 concentrations. T4 directly is important in neurological function and communication. As a result.. if your levels are off this can cause you issues as well.
As to why exercise can increase your alertness and such. Exercise produces natural endorphins and such that make you more alert and on guard it goes back to the predator prey .. fight or flight instinct we all have. In mild hypoT.. or suboptimal T4 patients.. this may be enough to correct things or mask issues. Done for now.
This meet your expectations. Must cook dinner, my son is making protests!
This of course is my non-MD hypothesis and researched opinion on the matter.. I forget to leave that out.