Role of the Pituitary Iodothyronine 5’Deiodinase Activity in the Negative Feedback by Thyroid Hormone upon TSH Release
It is widely accepted that triiodothyronine (T3) accounts for nearly all of the thyromimetic potency of thyroidal secretion. The nuclear thyroid hormone receptors bind T3 with > 10-fold higher affinity than thyroxine (T4), and the intracellular concentration of T4 is not enough to occupy more than 10f of these receptors—a substantial fraction of which may actually be non-specifically bound. About a decade ago, this and the relatively rapid exchange of plasma T3 with the receptor, led to the concept that the thyroid status of the tissues was closely reflected by the plasma concentration of T3 (1).
KeywordsThyroid Hormone Iodine Deficiency Iopanoic Acid Pituitary Homogenate Nuclear Thyroid Hormone Receptor
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