Re: Caeliacs and autoimmune thyroid disease
It is possible to have hypothyroidism ('iatrogenic hypothyroidism') after treatment with radioactive iodine but this is usually temporary (lasting about 3 months) and is typically discovered on screening before it causes symptoms. [The term 'Hashimoto's' refers to a particular type of hypothyroidism - Hashimoto's can't be caused by radioactive iodine therapy]
Both Graves' and Hashimoto's are associated with other autoimmune conditions like Coeliac disease, but this is relatively uncommon. Coeliac disease normally presents with mild intermittent diarrhoea and abdominal discomfort on a background of weakness and fatigue (it's caused by an intolerance to foods containing gluten eg. wheat, rye and barley), but this doesn't quite sound like what you've experienced in the past.
The diagnosis of Coeliac disease can be made by biopsy (taking small tissue samples) during your endoscopy. If there is clinical suspicion of CD, your doctor can also take some blood to check for specific antibodies associated with the condition.
Hope this helps.