A histochemical analysis of gamma-glutamyl transpeptidase (GGT) activity was performed on 42 cases of various human thyroid diseases. In contrast to the negative reaction for GGT in the normal thyroid tissues, a rather widespread distribution of activity was demonstrated in diseased thyroids. Among thyroid neoplasms, papillary carcinoma showed the strongest and most stable activity, while a more variable activity occurred in follicular carcinoma. Anaplastic carcinoma and medullary carcinoma were negligible in the activity. In non-neoplastic thyroid diseases, the activity was localized in distribution and usually less pronounced, as compared with the neoplastic lesions.
This study suggests that the appearance of GGT activity in thyroid tissues reflects not only proliferative or regenerative changes of the follicular epithelium but also functional aspects of the lesions.