PITUITARY REGULATION OF THYROID ACTIVITY

Abstract

ABSTRACT Under normal conditions the thyroid function is mainly controlled by the content of thyroid hormone in plasma. If the level is too low, this acts as a stimulus for the pituitary production of thyrotrophic hormone. If it is too high, the opposite effect prevails. Administration of salicylate or dinitrophenol influences the thyroid function in a way which appears to contradict the existence of a regulating mechanism of this kind. However, evidence is presented which is consistent with the view that it is not the total content of thyroid hormone in the plasma, but its content of free, non-protein-bound thyroxine that regulates the pituitary effect on the thyroid.