Endocrine Abstracts

Riedel thyroiditis is a rare chronic inflammatory disease of the thyroid. It is characterized by replacement of normal parenchyma with dense fibrotic tissue. Peripheral tissues might also be affected and this may cause airway obstruction, dysphagia, recurrent laryngeal nerve palsy and hypoparathyroidism. We report a patient with toxic adenoma previously treated with radioactive iodine and histopathologically confirmed Riedel thyroiditis.

Case: A 61 years old male patient was referred because of subclinical hyperthyroidism. He did not have any obstructive symptoms. In physical examination, a 3×2 cm nodule was detected in the left lobe. Serum TSH, fT₃, fT₄ and thyroglubulin levels were 0.047 μIU/ml (0.4–4 μIU/ml), 2.04 pg/ml (1.57–4.71 pg/ml), 1.03 ng/dl (0.85–1.78 ng/dl), and 6.31 mg/dl (1.15–35 mg/dl) respectively. Antithyroid peroxidase, antithyroglobulin and thyroid stimulating antibodies were negative. Thyroid ultrasonography revealed a 15×20×28 mm isoechoic nodule located in superior and mid portions of left lobe. Ultrasonographically the nodule had a thin hypoechoic halo, cytic degeneration areas and macrocalcification. Thyroid scintigraphy showed an active nodule with extranodular suppression of thyroid parenchyma. Uptake was 10% after 4 h and 25% after 24 h of I¹³¹ administration. The nodule was evalueated with fine needle aspiration biospy and cytology was benign. The patient was treated with 20 mci radioactive iodine for toxic adenoma. In follow up, since nodule diameter increased significantly after 6 months, total thyroidectomy was performed. In histopathological examination, there was marked fibrosis in stroma and some atrophic glands in thyroid tissue. Fibrosis was extending to the surrounding fat tissue and focal chronic inflammatory cells were observed around middle sized veins. With these findings, the patient was diagnosed to have Riedel thyroiditis.

Conclusion: Riedel thyroiditis is a very rare disease of the thyroid gland. To our knowledge, this is the first case with coexistent toxic adenoma and Riedel thyroiditis reported in the literature.