The aging thyroid. II. An immunocytochemical analysis of the age-associated lesions.

This study utilizing immunocytochemical techniques consists of two segments, 1) an analysis of the changes with age in the hormone content of normal, involuting, macro- and microfollicles, as well as calcitonin (C) cells, and 2) an analysis of the components of the lesion characteristic of lymphocytic thyroiditis. Involuting and macro- (cystic) follicles show a decline in hormone content with age, while microfollicles show a variable pattern with some showing a high and others a low content, as well as some showing an absence of hormone. There also appears to be an increase with age in hormone-containing C cell micronodules, but we were unable to demonstrate a decline in hormone content of individual C cells. Studies on the in vivo binding of immunoglobulins, as an indicator of thyroid antibody binding, showed an increase with age in IgG and IgM binding to follicular epithelium. Much stronger reactions were observed in the epithelium of microfollicles than in that of involuting or macrofollicles. There were also examples of presumptive in vivo antibody binding by C cell micronodules. We were unable to demonstrate an imbalance of helper/suppressor T cell ratio in the thyroiditis lesion, but did find that some lymphocytes contain thyroid hormones, suggesting that the latter may act as cytokines and assist in the perpetuation of the lesion. The epithelial expression of human lymphocyte antigens (HLA) was strong in microfollicles and weak or absent in involuting or macrofollicles in sections with lymphocytic thyroiditis. It was also strong in the epithelium of a microfollicular adenoma without a lymphocytic infiltrate while weak or absent in the epithelium of adjacent normal follicles.(ABSTRACT TRUNCATED AT 250 WORDS)