DISTURBANCE OF THYROIDAL IODINE-METABOLISM IN BB W RAT/

To investigate the thyroid function in Bio-Breeding Worcester (BB/W) r ats, we have examined the iodine metabolism, serum TSH and thyroid hor mone levels in 8- and 16-week-old BB/W and normal Wistar (W) rats. At 8 weeks of age, serum TSH levels were significantly higher in BB/W rat s than in W rats, although there was no difference in the serum levels of free T3 and free T4. Furthermore, the thyroidal radioactive iodine incorporation at 48 h was significantly lower in BB/W rats, suggestin g that they might have some defects in iodine organification. At 16 we eks of age, serum TSH levels were also significantly higher in BB/W ra ts than in W rats. Furthermore, serum TSH levels in 16-week-old BB/W r ats were significantly higher than in 8-week-old BB/W rats. The thyroi d weight was significantly greater in BB/W rats, probably due to the i ncreased serum TSH. The thyroidal radioactive iodine uptake at 48 h an d the iodine content in the thyroid homogenates were significantly low er in BB/W rats. These results suggest that BB/W rats have some defect in iodine metabolism resulting in impaired thyroid hormone synthesis.