A young female patient suffering from Graves' disease is presented, who raised some diagnostic and therapeutic dilemmas after being diagnosed with subclinical hyperthyroidism following total thyroidectomy. This 20-year-old female patient, carrier of HLA B8 DR3 genes, was referred to our hospital for total thyroidectomy after developing severe leukopenia on both methimazole and propylthiouracil therapy. A high postoperative titer of thyrotropin receptor antibodies and positive scintigraphy finding of the pyramidal lobe and remnant thyroid tissue in the left thyroid lobe led to the administration of radioiodine. Despite further enlargement of the remnant thyroid tissue on post-radioiodine scintiscanning, the patient is currently euthyroid, with normal thyroid-stimulating hormone levels; however, her long-term prognosis remains uncertain.