When Hashimoto's patients developing hypothyroidism, an under-active thyroid gland, go through Hashitoxicosis-temporary hyperthyroidism (overactive) they usually only register a slight difference in blood labs or only a mild indication of hyperthyroidism on them due to progressive hypothyroidism trying to take over. In other words, though these patients alternate between hyperthyroidism and hypothyroidism, it is temporary so that lab results of their thyroid hormone levels can at times be neutral or show only mild hyperthyroidism. Once hypothyroidism does take over, they will need thyroid hormone replacement as a lifelong treatment.

With Graves', it settles in long enough to register as full blown hyperthyroidism on blood tests. This plus a high elevation of TSI antibodies points to definitive diagnosis of Graves' Disease. Some doctors try an anti-thyroid drug or what's called a "PTU" (propylthiouracil and Carbimazole) that slows thyroid hormone production for Graves’-hyperthyroidism and after a trial of it, will wean the patient off of it after a few months and see if the hyperthyroidism resolves. If not, they will then opt for RAI ablation (Radio Active Iodine destruction of the gland) or a thyroidectomy (surgical removal). Many will first try a beta-blocker to see if it controls the hyperthyroid symptoms before going on to a PTU or a combination of the two.

If you are recommended for getting a thyroidectomy Vs RAI ask your doctor to go over the procedure with you (risks etc...), or to refer you to a doctor who can, so you can weigh the two options. You might also ask him about anti-thyroid medications if he feels they are another possible option in your case. In short, I would say overt hyperthyroidism on blood lab test results definitely points to Graves' disease. It is not that unusual for offspring of autoimmune thyroid disease parents to develop one or the other because the two diseases (Hashimoto's thyroiditis & Graves' Disease) are more closely related than most people realize.