I had a total thyroidectomy and have gained 20 pounds despite being in a pharmaceutical hyperthyroidism state to treat papillary carcinoma. ?

It is likely from Fo: It is likely due to excess of calorie intake. Low thyroid levels do not cause this kind of rapid weight gain. You need to start cutting on your Food/calories consumed and begin to do some daily exercise. Start with a daily walk for 20-30 minutes and eat mostly plant based foods and cut down on meats, dairy products and all fast foods and foods with high sugar content. Aim for losing 1 pound/wk