Chronic thyroiditis: thyroid function and histologic correlations in 601 cases

Six hundred one patients with histologically proven "chronic thyroiditis" were assessed for the correlation of thyroid function to histologic findings. The histology of chronic thyroiditis was classified into four groups (oxyphilic, mixed, focal, and hyperplastic), and the thyroid function of patients was divided into hyperthyroid, euthyroid, latent hypothyroid, and overt hypothyroid, based on the laboratory data of serum triiodothyronine (T3), thyroxine (T4), and thyrotropin (TSH) levels, as well as thyrotropin-releasing hormone (TRH) tests. In the oxyphilic group (137 cases), 116 (85%) of the patients were classified as hypothyroid: 52 (38%) as latent hypothyroid and 64 (47%) as overt hypothyroid. In the mixed group (161 cases), the thyroid function of the patients varied. Thirty-seven (23%) of the patients were classified as hyperthyroid, 61 (39%) as euthyroid, 54 (33%) as latent hypothyroid, and nine (5%) as overt hypothyroid. In this group thyroid function was intimately related to the ratio of replacement by hyperplastic-changed follicles and oxyphilic-changed follicles. In the focal group (149 cases), 123 (83%) of the patients were classified as euthyroid, while 22 (14%) were classified as latent hypothyroid. The frequency of latent hypothyroid patients increased in parallel with the severity of cell infiltration. In the hyperplastic group (154 cases), 130 (85%) of the patients were classified as hyperthyroid. In this series 19 patients under 10 years of age were included, and no difference in the distribution of histologic varieties was observed between juvenile and adult patients. Thyroid needle biopsy is a useful and safe tool, not only for the histologic diagnosis of chronic thyroiditis, but also for the evaluation of thyroid function and the identification of causes for hyperthyroidism or hypothyroidism.