Endocrine Abstracts

Introduction: Riedel's thyroiditis is a rare chronic inflammatory disease of the thyroid characterised by an invasive fibrotic process.

Case report: A 48-year old lady with newly diagnosed profound hypothyroidism was started on thyroxine and referred due to a rapidly enlarging goitre. Examination revealed a hard fixed goitre in an euthyroid patient. Thyroglobulin (titre 1: 10,000) and thyroid peroxidase (titre 1: 100,000) antibodies were strongly positive, ESR was 98 mm/hour. Thyroid and renal function and calcium were normal. A tru-cut biopsy (instead of open biopsy) confirmed Riedel's struma with abundant inflammatory cell infiltrate. Regression of the goitre and reduction of antibody titres occurred after starting Prednisolone 30 mg daily, which was stopped after 10 months. Six months later she presented with renal failure due to retroperitoneal fibrosis that was successfully treated by reinstitution of steroids at the same dose and ureteric stenting acutely. Steroids were withdrawn after 8 months and she remains well on thyroxine replacement.

Discussion: Very high titres of thyroid antibodies and hypothyroidism predating the development of goitre suggest co-existence of Hashimoto's thyroiditis and Riedel's thyroiditis. Tru-cut biopsy obviated the need for open thyroidectomy and biopsy, which carries a higher risk in Riedel's thyroiditis. A predominantly inflammatory as opposed to fibrotic thyroid histology may predict good response to steroids in Riedel's thyroiditis. Modest doses of steroids were successfully used on both occasions. Relapse following steroid withdrawal may not only be in the thyroid but also at other sites, thus necessitating follow-up and clinical vigilance.