Brief Answer: Graves disease can not derive from Hashimoto thyroiditis, once it has entered into hypo functional and atrophic phase. Detailed Answer: Hello, Thank you for using HCM. Both Hashimoto thyroiditis and Graves disease are disorders of the thyroid gland with autoimmune etiology. Thyroid peroxidase (TPO) antibodies are increased in more than 90 % of the patients suffering from Hashimoto s thyroiditis, while TSH- receptor antibodies are found to be positive in 60-80 % of the cases with Graves disease. Thyroiditis Hashimoto is a inflammation of the thyroid gland which leads to persistent hypothyroidism, expressed clinically with: sleepiness, dry hair and skin, cold intolerance, hair loss, difficulty concentrating, poor memory, constipation, weight gain, muscle cramping etc. Most of which you have probably experienced when you were not under hormone replacement therapy. It is associated with atrophic (small) thyroid gland. Meanwhile, morbus Graves is associated with hyperthyroidism, experienced as: heat intolerance, irritability, nervousness, rapid heart rate(palpitations), excessive sweating, tremor, and weight loss, etc. It is associated with enlarged thyroid gland, 2-3 folds to normal. So they are both with autoimun ethiology, but they are different in functional activity of the thyroid gland ( hormone levels), in structure (differences seen echografically, size structure, etc), the symptoms, and as a consequence, the treatment changes too. In your case, the treatment needed is the hormone replacement therapy (Levothyroxine), while in Graves disease, the patients need to take anti thyroid drugs such as propylthiouracil, methimaszole, etc. Returning to your principal concern : No. Graves disease can not derive from Hashimoto thyroiditis, because the thyroid gland once is turned into hypo functional and atrophic phase , which are definitive changes following the acute phase, can not be any more hyper functional and even normo functional (normal hormone levels in blood). Which means you need to take hormone replacement therapy all the time, monitoring the TSH, fT3, fT4 levels in blood periodically. And once the thyroid gland is atrophic it can not turn to hypertrophic any more. This is the usual evolution of Hashimoto thyroiditis , and the most probable in your case as you have 2 years now, diagnosed with this disease. Hope this may be helpful for you. Let me know if you need more clarifications. Otherwise please close and rate the answer. Kind Regards, Dr. Juarda