Hashimoto's thyroiditis or chronic lymphocytic thyroiditis is an autoimmune disease
in which the thyroid gland is attacked by a variety of cell- and antibody-mediated immune processes.
Automimmune disorders that occur with increased frequency in patients with Hashimoto's thyroiditis include insulin-dependent diabetes mellitus, myasthenia gravis, celiac disease, pernicious anemia, vitiligo, rheumatoid arthritis
, systemic lupus erythematosus
, scleroderma etc.
Since you are having history of long standing diarrhea,there is a strong suspicion of having celiac disease.You must consult a gastroenterologist
and get a colonoscopy and biopsy for the diagnosis and treatment.