EFFECT OF THE C-TERMINUS OF TSHR ON T4 AND TRAB EXPRESSION IN BALB/C MICE.

CONTEXT: The expression of TSHR-C on the serum tetraiodothyronine (T4) and TSH receptor antibody (TRAb) levels are rarely studied.

OBJECTIVE: The effect of TSHR-c on T4 and TRAb levels and concomitant thyroid histological changes in mice was investigated.

DESIGN: Animal experimental study.

SUBJECTS AND METHODS: Female BALB/c mice at 6-8 weeks of age were immunized with the thyroid stimulating hormone receptor antigen C-terminus (TSHR-C), and randomly divided into control group (treated with the corresponding concentrations of normal saline) and four experimental subgroups: TSHR-c1 subgroup (4 µg), TSHR-c2 subgroup (6 µg), TSHR-c3 subgroup (8 µg) and TSHR-c4 subgroup (10 µg). Serum T4 and TRAb levels were determined.

RESULTS: The serum T4 level decreased significantly in the experimental mice as the concentration increased. All the experimental mice were positive for serum TRAb (experimental groups: 40 positive/40, 100% vs . control group: 3 positive/10, 30%) compared to the control group (P =0.000). HE staining showed that the follicles in the control mice were composed of small to medium-sized round follicles, whereas the follicles in the experimental mice were irregularly enlarged under light microscope.

CONCLUSIONS: TSHR-c immunization resulted in thyroid hormone changes like those observed in hypothyroidism, probably due to the induction of TRAb generation.