I have different opinion.
Besides thyroid, more likely possibility is an underlying autoimmune disorder.
This can be systemic lupus, or systemic sclerosis.
Also Inflammatory bowel disorders like Crohn' disease can cause symptoms outside the intestine as well.
You will need following blood tests: ANA, ds DNA, anti ro, anti la, anti scl70, anti sacharomyces, ancas,
You will also need upper GI endoscopy and colonoscopy for biopsies of the intestine.
You should consult with a GI doc and a rheumatologist.
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