Abstract
The present study was made to evaluate the hypothalamo-hypophyseal control of thyroid.
The results obtained were as follows :
In euthyroid rabbits, injected with 131I, the posterior pituitary had more affinity for 131I than that in median eminence and anterior pituitary.
In hyperthyroidism, produced by the administration of TSH and thyroid hormone, 131I uptake in these tissues was remarkably increased. On the contrary, in hypothyroidism, by the thyroidectomy and administration of MTU of cortisone, concentration of the 131I in these tissues was significantly reduced.
As to the hypothalamic neurosecretory function and TSH secretion, in hyperthyroidism, these functions were inhibited, while they were stimulated in hypothyroidism.
These results revealed that the sites where 131I was concentrated, corresponded to regions of the neurosecretory system, and also that the concentration of 131I by the posterior pituitary and median eminence was associated with neurosecretory phenomena. This may be related to the functional control of the TSH secretion by the anterior pituitary.
