Somatotropic function of the adenohypophysis in hyperthyroidism

: Changes in the adenohypophyseal somatotropin function and the site of their origin were studied in experimental rats with hyperthyrosis. It was determined that the adenohypophyseal somatotropin content and biosynthesis were sharply reduced. After repeated somatotropin injections these indices remained unchanged. In vitro the somatotropin-releasing activity of the hypothalamic extracts off hyperthyroid rats is enhanced, whereas somatotropin release into the medium, obtained from the adenohypophyses of hyperthyroid animals, is lowered under the extract effect. It is concluded that a decrease in the adenohypophyseal somatotropin function is caused by loss of somatotropic cell sensitivity to the action of the hypothalamic regulation factors.