TG and thyroid gland carcinoma: The mechanism of this association is not thought to be similar to the thymic hyperplasia demonstrated after chemotherapy or after stress conditions or acute infections, when hyperplasia happen because of an immunological reaction.22 It seems that l-thyroxin hormone therapy in supraphysiological doses is responsible for the thymic hyperplasia in patients with thyroid carcinoma.21 Heath et al,23 with the technique of reverse transcription and polymerase chain reaction from analyses of mRNA, showed the thymic expression of thyroglobulin (Tg) in embryonic mice and adult rats.