Endocrine Abstracts

Riedel’s thyroiditis (RT) is a rare, inflammatory-sclerosing disease of the thyroid gland, with dense fibrosis that replaces normal thyroid tissue and local extension to surrounding structures causing hypothyroidism and compressive symptoms. The etiology of RT remains unknown, and its treatment is still challenging in absence of guideline consensus. We report 7 patients seen in a department of Endocrinology between 2000 and 2023: 5 women and 2 men, mean age 46 (20–81) years. Patients had a slow-growing thyroid goiter (6/7) or a 3-cm hypoechogenic nodule (1/7), hypothyroidism (4/7) with anti-TPO antibodies (3/7). Serum C-reactive protein levels were increased (4/7), serum IgG4 levels were normal (4/4). A 20-year-old female presented sclerosing cholangitis treated with prednisone, azathioprine and ursodesoxycholic acid. RT was diagnosed on histological examen after thyroidectomy (2/7) or surgical biopsy (5/7). Postoperative evaluation with CT and/or 18 FDG PET scans showed heterogenous uptake of the thyroid tissue (5/7) but no extrathyroidal fibrosclerosis. Patients were treated with levothyroxine alone after thyroidectomy (2/7) or with systemic steroids (4/7), then tamoxifen (3/7) or rituximab (2/7) according to clinical and 18 FDG PET evaluation. Anti-inflammatory and immunosuppressive treatments were associated with control of the size, and a decrease of the uptake of thyroid tissue. During prednisone (1 mg/kg/day) treatment, the 81-year-old patient presented cervical tissue necrosis (past history of external cervical radiotherapy for a thyroid neoplasm 35 years earlier) and died of severe sepsis 45 days after surgery. After 2-year tamoxifen treatment, a 51-year-old woman developed pseudo-tumor of the orbits after tamoxifen withdrawal, with a significant improvement during prednisone (1 mg/kg/day) and tamoxifen (20 mg/day) combined treatment. After 4-year tamoxifen treatment, a 61-year-old woman presented a meningioma and several episodes of uterine bleeding accounting for tamoxifen withdrawal. During a mean 9-year follow-up of the patients, response of RT to medical treatment was observed, and imaging examens did not revealed extrathyroidal fibrosis. Based on the reported patients and review of the literature, first-line glucocorticoid and second-line tamoxifen treatments are indicated to control the inflammatory-fibrotic process: optimal dose and duration of treatments need further studies. In RT resistant to steroid and tamoxifen treatment, immunosuppressive molecules (rituximab, mycophenolate mofetil, azathioprine) need to be evaluated. Thyroid surgery should be limited to debulking in patients with tracheal or oesophageal compression, or is indicated in “refractory” RT with failure of medical treatment. RT has a good prognosis in most patients, but long-term follow-up is necessary to evaluate the risk of local relapse after withdrawal of medical therapy, and of the possible involvement of extrathyroidal fibrosclerosis.