Increased sensitivity of the thyroid in iodine-depleted rats to the goitrogenic effects of thyrotropin

In the present studies we have explored the possibility that the intrathyroid content of iodine might

George A. Bray

2011

Scholarcy highlights

  • Thyroid activity is regulated by two mechanisms; it varies directly with the level of circulating thyrotropin and inversely with the iodine content of the thyroid gland itself
  • Addition of 0.1% propylthiouracil to the low iodine diet before hypophysectomy increased the thyroid weight to 32.8 mg/100 g of body weight and depleted the thyroid of more than 99%o of its iodine
  • The addition of propylthiouracil or perchlorate to the diet of hypophysectomized, iodine-depleted rats did not change the weight of their thyroid glands, and neither drug inhibited or augmented the thyroid enlargement produced by thyrotropin
  • During treatment with thyrotropin the iodine content increased in thyroid glands from rats that had been severely depleted of iodine before hypophysectomy
  • The present studies demonstrate the extreme sensitivity of the iodine-depleted thyroid to the goitrogenic effects of thyrotropin, and support the concept that enlargement of the thyroid is inversely related to iodine content. 3 mU of thyrotropin were given to 100 g rats in divided doses each day, such that each dose contained only 1 mU of TSH
  • If this entire dose were immediately absorbed into a blood volume equivalent to 10% of the body weight, the concentration could reach a level of 0.1 mU/ml, a value five times higher than that of 0.02 mU/ml for serum
  • Albert et al , on the contrary, found that thiouracil potentiated the effects of 400 ug of TSH in chicks fed the goitrogen, and Alexander and Wolff observed that 10 U of TSH daily for 14 days produced somewhat larger thyroid glands in rats which were receiving propylthiouracil

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