Graves disease after radioactive iodine treated toxic adenoma

Joana Vinhais; Pereira Beatriz R; David Verissimo; Catarina Ivo; Martins Ana Claudia; Mafalda Marcelino; Dolores Passos; Luis Lopes; de Castro Joao Jacome; e Silva Joao Nunes

doi:10.1530/endoabs.110.EP1606

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Endocrine Abstracts (2025) 110 EP1606 | DOI: 10.1530/endoabs.110.EP1606

ECEESPE2025 ePoster Presentations Thyroid (198 abstracts)

Graves disease after radioactive iodine treated toxic adenoma

Joana Vinhais ¹ , Beatriz R Pereira ¹ , David Verissimo ¹ , Catarina Ivo ¹ , Ana Cláudia Martins ¹ , Mafalda Marcelino ¹ , Dolores Passos ¹ , Luís Lopes ¹ , João Jácome de Castro ¹ & João Nunes e Silva ¹

Author affiliations

¹Portuguese Armed Forces Hospital, Endorinology Department, Lisbon, Portugal

JOINT3433

Background: The most frequent causes of hyperthyroidism are Graves disease (GD) and toxic thyroid adenomas. The development of postradioiodine immunogenic hyperthyroidism/GD after radioiodine therapy (RAI) for toxic adenomas occurs in approximately 1.4% of the patients and seems to be more common in patients with increased anti-TPO levels pre-treatment. This effect occurs on average 4.6 months after RAI.

Case Report: A 49 years-old women was evaluated for thyroid nodular disease and hyperthyroidism on our endocrinology clinic in May 2021. She denied compressive symptoms, excessive sweating, loss of weight, or altered intestinal pattern, but confirmed occasional palpitations. No relevant personal or family history. Clinical exam was normal and exophthalmia not present. Cervical palpation unveiled bilateral goitre with palpable nodules bilaterally, 3 cm each, mobile on swallowing and absent cervical adenopathies. Biochemical evaluation reported TSH 0.02, FT4 1.07 (0.8-1.76), FT3 3.84 (1.88-3.18), ATG 499 (<4.11), ATPO 96.3 (<5.61), TRAb 1.2 (<1.8). Cervical ultrasonography (US) showed a multinodular goitre, EU-TIRADS 3 nodules, 33 mm and 13 mm on right lobe, 33 mm and 14 mm on left lobe, and 20 mm and 14 mm on isthmus. Thyroid scintigraphy revealed a hot nodule in the inferior right lobe. Patient initiated methimazole and performed fine needle aspiration biopsy of the cold nodules, revealing a benign cytology. The toxic nodule of the right lobe was treated with 10mCi of RAI I-131 achieving clinical and biochemical euthyroidism (TSH 1.54, FT4 1.05, FT3 3.02). One year later she presented with sinus tachycardia on clinical exam, but otherwise without hyperthyroidism signs or symptoms, and analysis reported TSH 0.09, FT4 1.27. Thyroid scintigraphy was repeated and revealed hypofixation of radiocontrast in the lower half of right lobe, and hyperfixation bilaterally in the remaining parenchyma. Laboratory workup reported TSH 0.011, FT4 1.44, FT3 5.37, TRAb 2.5. After discussion with the patient and in multidisciplinary reunion, total thyroidectomy was performed for definitive treatment of Graves disease.

Conclusion: This patient presented with GD 12 months after RAI therapy for toxic adenoma. This rare case highlights the importance of maintaining vigilance of patients after RAI, especially those with elevated anti-TPO.