Hello and welcome to ‘Ask A Doctor’ service.
I have reviewed your query and here is my advice.
The TSH level in your blood reveals how much T4 your
pituitary gland is asking your thyroid gland to make.
The elevated TSH result means
Hypothyroidism or underactive thyroid.
The most common cause of hypothyroidism is Hashimoto's thyroiditis.
In my opinion ,this is your exact diagnosis.
In Hashimoto's thyroiditis, the body mounts an immune reaction against its own thyroid gland tissue, leading to inflammation and the destruction of the gland (thyroiditis).
So,your TSH level is high because your Pituitary gland is asking your thyroid gland to make more Thyroid hormones ,but the inflammated thyroid can not produce hormone any more and it is vital to take the thyroid
hormone replacement therapy.
In your circumstances the Hypothyroidism is the result of the insufficient dosis of
thyroid hormone replacement therapy or
Levothyroxine.
The result means that you need to adjust the actual dosis of Levothyroxine.
The increased dosis of Levothyroxine will help you to normalise your TSH result and feel better.
Hope i have clarified your doubt.
Let me know if i can assist you further.