My husband has just recently been diagnosed with hyperthyroidism which we were told, in his case, was caused by Grave's Disease. However, I am very confused because my husband weighs 420 pounds and falls in to the morbidly obese category. Everything I have read says that hyperthyroidism and Grave's Disease causes unintentional weight loss. How is this possible? His blood test results are TSH - 0.008 UIU/ML, Total T3 - 79.67 NG/DL, and his Free T4 is 1.81 NG/DL. I also read for a diagnosis of hyperthyroidism, one or both the T3 or T4 must be high. However, his TPO test came back high which is why, I'm guessing, the endocrinologist believes he has Grave's disease. The TPO result was 47.5 IU/ML. I'm baffled as to how someone who is obese can have hyperthyroidism. Could there be something else here that is causing the hyperthyroidism besides Grave's Disease?