Is lymphocytic thyroiditis a unique type or merely a type of Hashimoto's thyroiditis?

Objective of the study was to clarify the role of apoptosis in the pathogenesis of lymphocytic thyroiditis (LT) and the existence of difference between Hashimoto's thyroiditis (HT) and LT.

We evaluated levels of antithyroglobulin and antithyroperoxidase antibodies, the apoptosis by in situ Cell Death Detection-TUNEL and the expression of Bcl2 and Bax by immunohistochemistry in thyroid tissues from 16 patient with HT, 10 with LT and 10 with euthyroid goiter-EG (control group).

It was found that apoptosis of thyrocytes in HT (mean 3.05%, SD 1.29%) and LT (mean 2.70%, SD 1.17%) was statistically significantly higher than EG (mean 0.56%, SD 0.23%), but the difference in the percentage of thyrocytes between HT and LT was not statistically significant. In HT the percentage of apoptotic infiltrating lymphocytes (mean 0.59%, SD 0.23%) was smaller than in EG (mean 2.26%, SD 1.42%), but it showed no significant difference in comparison to LT. The expression of Bax in infiltrating lymphocytes in HT (mean 0.72%, SD 0.34%) was statistically significantly higher than LT (mean 0.11%, SD 0.06%). The level of thyroglobulin was lower in HT compared to LT (P<0.01) and compared to EG (P<0.01). The level of antithyroglobulin/antithyroperoxidase antibodies was higher in HT compared to LT (P<0.01) and compared to EG (P<0.01). There was no statistically significant difference in the level of thyroglobulin and level of antibodies between LT and EG.

These results suppose that apoptosis represents one of significant mechanisms in the pathogenesis of both HT and LT and that LT probably differs from HT.