THYMIC HYPERPLASIA IN PATIENTS WITH GRAVES-DISEASE - IDENTIFICATION OF THYROTROPIN RECEPTORS IN HUMAN THYMUS

Thymic size and density were studied in 23 untreated patients with Gra ves' disease and 38 control subjects using computed tomography. Both t hymic size and density were higher in untreated patients with Graves' disease than in control subjects in the age-matched group. After treat ment with antithyroid drugs, both thymic size and density were signifi cantly reduced, with a concomitant decrease in thyrotropin receptor an tibodies, PCR of human thymic cDNA using primers for human thyrotropin receptor amplified a fragment in a size expected for the receptor, an d its nucleotide sequence was identical to human thyrotropin receptor cDNA in the thyroid, Northern blot analysis of human thymic poly(A)(+) RNA demonstrated the presence of the full length form of thyrotropin receptor mRNA, Western blot analysis of human thymic membrane using an ti-thyrotropin receptor peptide antibodies demonstrated a band of simi lar to 100 kD that was also observed in the thyroid membrane, Immunohi stochemistry of thymic tissue using mouse antihuman thyrotropin recept or monoclonal antibodies demonstrated the immunostaining of epithelial cells. These results indicate that thymic hyperplasia is apparently a ssociated with Graves' disease and suggest that thymic thyrotropin rec eptor may act as an autoantigen that may be involved in the pathophysi ology of development of Graves' disease.