Hello, Though your thyroid profile looks normal, you could still be hypothyroid as sometimes anti-thyroid antibodies do the harm. It is in the hypothyroid state that weight gain occurs. Low doses of thyroxine may be given as a test for three months followed by an evaluation, if all reasons for obesity are excluded. Thyroid cancer does not occur. The drug should not be used for losing weight alone, as it has some unwanted side effects like increased blood sugar levels, increased hair loss, decreased bone density and an increased load on the heart function initially. You should consult an endocrinologist for advice. Take care.