Hello! Thanks for putting your query in HCM. I am a Gastroenterologist (DM).
What you all have to do is:
1. Make yourself euthyroid by titrating the dose of thyroxine
2. I think you need colonoscopy
examination and may be a biopsy
if any lesion is found as there is MARKED thickening of sigmoid wall, moreover as there was blood in stool
I hope I have answered your query and this will help you. Remain in touch and get-well soon.