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and lower leg pain are not related to the thyroid
problem.In thyroid your weight will increase since you have hypothyroid.As for the deficiency of vitamin B12
if it is severe it may cause pain in leg but not in throat.If the throat pain is internal it may be related to tonsil
infection and if the pain is external then it can be thyroid if there is a swelling or a cyst.Get examined by your doctor and he will treat you accordingly.