Interaction between the hypothalamic-hypophyseal system and thyroid gland at different age periods

Abstract

Age differences in interaction between the hypothalamic-hypophyseal system and the thyroid gland were studied with consideration to both direct and feedback control. In old age significant disturbances affect both direct and feedback components of this system; the sensitivity of thyroid tissue to TSH and of the hypothalamus and pituitary to the action of T4 is increased. The increased sensitivity of the hypothalamic-hypophyseal system to T4 is largely determined by activation of the deiodination of T4 by the adenohypophysis. The reactivity of the thyroid gland and hypothalamic-hypophyseal complex to the corresponding factors is reduced.