MON-353 Total Thyroidectomy Is Not Definitive Therapy in All Graves’ Cases: Should Scintigraphy Be Considered in All Graves’ Patients Prior to Thyroidectomy?

Abstract Disclosure: A. Numi: None. A. Musleh: None. E. Afroze: None. J. Chukwu: None. M.T. Rauf: None. Introduction: Ectopic thyroid tissue (ETT) in patients with Graves’ disease is a rare finding; however, when present it might lead to a different treatment approach. Here we present a case of concomitant Graves’ disease (GD) in eutopic and ectopic thyroid, where ETT was diagnosed only after a total thyroidectomy was performed. Clinical case: A 41-year-old female initially presented to her primary care physician with symptoms of thyrotoxicosis, including unintentional 30-pound weight loss, palpitations, and tremor. Initial thyroid function tests showed TSH <0.01 mcIU/ml (n 0.45-5.33 mcIU/ml), free T4 2.87 ng/dl (n 0.61-1.85 ng/dl), free T3 11 pcg/ml (n 2.1-4.1 pcg/ml), and thyroid peroxidase (TPO) antibodies >1000 IU/ml (n <40 IU/ml). Despite referral to endocrinology, the patient was lost to follow-up. Upon re-evaluation two years later, her thyrotoxicosis had worsened, with persistently high TPO antibodies. A thyroid ultrasound revealed diffusely enlarged, hyperemic thyroid tissue and two TI-RADS-4 nodules, one of which underwent fine needle aspiration and was benign. The patient preferred to have definitive treatment, and therefore was referred to a high-volume thyroid surgeon who recommended total thyroidectomy. Endocrinology saw her preoperatively, and started her on methimazole after thyroid stimulating immunoglobulin (TSI) was found to be positive at 28.5 IU/L (range <10 IU/L). Postoperative pathology was consistent with GD. She was started on levothyroxine following thyroidectomy; however, despite multiple dose adjustments with eventual discontinuation, the patient continued to experience thyrotoxicosis with a persistently positive TSI at 7.95 IU/L even 7 months post surgery. A subsequent iodine-123 whole-body scan with SPECT-CT identified multiple foci of ETT including multiple nodules in the anterior midline lower neck (1 x 1 cm in size), upper mediastinum inlet (1.8 x 1.1 cm) and anterior mediastinum (3.8 x 1.7 cm). Although iodine-131 ablation was offered, the patient achieved remission with monitoring alone. Conclusion: ETT is a rare condition, occurring in about 1 in 100,000-300,000 patients, often due to improper embryonic migration. It is typically found at the base of the tongue, but can rarely occur in the mediastinum. ETT is usually non-functioning, with hypothyroidism being a more common presentation. Hyperthyroidism, especially in conjunction with GD, is exceedingly rare, with only 14 documented cases involving both eutopic and triple ETT. Current guidelines suggest no further evaluation beyond TSI when GD is clinically evident. However, this case suggests that preoperative thyroid scintigraphy and SPECT-CT could alter management in patients with GD, potentially identifying ETT and avoiding incomplete therapy with thyroidectomy. Should this approach be considered universally in GD cases prior to thyroidectomy to rule out ETT? Presentation: Monday, July 14, 2025