Further observations of the hypothalamic control of the thyroid gland.

Abstract

(1) After placing the lesions in the anterior, middle and posterior hypothalamus of rats with the Krieg's stereotaxic machine, and the apparatus devised by the Brain Research Institute of Tokyo University, MTU or TRF was administered for 3 and 5 consecutive weeks, and the weight of pituitary and thyroid, I131 uptake of the thyroid, T/S ratio of I131 concentration and the histological changes in thyroid and hypophysis were investigated.(2) When the lesions extended from the rostrum of the median eminence to the frontal area in the hypothalamus, both the thyroid and the pituitary weight decreased, the thyroidal function was slightly depressed, and the goitrogenic response to MTU was prevented. However, when TRF was given, the weight and function of the thyroid remarkably increased.(3) When the lesions were placed in the middle and posterior hypothalamus, scarcely any depression was observed either morphologically or functionally. Depression was seen only when the lesions involved the median eminence. The goitrogenic effect of MTU was evidently observed. The administration of TRF produced both morphological and functional activation of the thyroid together with enlargement of the hypophysis.(4) A minute (0.2cc), small (0.5cc), medium (1.0cc) and large dose (2.0cc) of TRF were given to both intact rats and those with effective lesions in the anterior hypothalamus. In the case of the minute and small dose a remarkable increase was not seen in the weight of the thyroid and the uptake of the thyroid, but the increase was observed only in the case of the medium and the large dose. By contrast, T/S I131 accumulation ratio was evidently increased by the minute dose, and the increase became still more pronounced when larger doses were given.(5) It was discussed that the regulatory factor of TSH secretion would be TRF, a neurohumor elaborated in the anterior hypothalamus and excreted in urine.