THE PITUITARY AND THE THYROID 



tary of the thyroidectomized animal has not been deter- 

 mined. 



According to Kuschinsky (1933) and Hohlweg and Junk- 

 mann (1933), treatment of the rat with thyroxin reduces the 

 amount of thyroid-stimulating hormone in the pituitary.' 

 Livingston (1914) prevented pituitary hypertrophy in thy- 

 roidectomized male rabbits by administering thyroid gland. 

 These findings are in harmony with the view that thyroxin 

 lessens the formation of thyroid-stimulating hormone. The 

 absence of the thyroid, however, does not facilitate the for- 

 mation of an increased amount of thyroid-stimulating hor- 

 mone. 



The effects of hypophysectomy. — Following hypophysectomy 

 or the removal of the pars glandularis the thyroid becomes 

 inactive and even atrophic (Aschner, 191 2; Ascoli and Leg- 

 nani, 1912; Houssay, 1916; Dott, 1923; Smith, 1926, 1930; 

 Koster, 1929; Houssay, Biasotti, and Mazzocco, 1931; and 

 McPhail, 1935). Histologically this is indicated by the flat- 

 tened appearance of the epithelium and the persistence of 

 deeply stained colloid. The diameter of the alveoli may be 

 increased or diminished. Grossly the thyroid of the hypophy- 

 sectomized animal is much smaller and appears less vascular 

 than that of the control animal. These changes are illus- 

 trated in Figure 46, showing the gross appearance of the thy- 

 roids of the littermate normal and hypophysectomized rats 

 of Figure 1 1. Photomicrographs of the thyroids of Figure 46 

 are reproduced in Figure 47. As will be pointed out below, 

 the administration of anterior pituitary as tissue or extract 

 restores the thyroid of the hypophysectomized animal to a 



9 Severinghaus and others (1934) studied the effects of thyroid-feeding or thy- 

 roxin-injection on the histologic appearance of the male rat's pituitary. A similar 

 study was made by Thomson and others (1934), who administered a thyrotropic 

 extract repeatedly to female rats. In both sets of experiments the basophils ap- 

 peared like "castration"-cells; in addition, changes in the oxyphils and the reserve 

 cells or degenerative changes were described. A marked atrophy of the ovaries was 

 observed in the rats used by Thomson and his colleagues (also see Campbell and 

 others, 1934). 



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