CHAPTER VII 



THE INTERRELATIONSHIP BETWEEN THE 

 PITUITARY AND THE THYROID 



SINCE 1888, when Rogowitsch (or Rogowitch) reported 

 that thyroidectomy in the rabbit was followed by def- 

 inite changes in the anterior-lobe cells and possibly by 

 hypertrophy of the pars glandularis (1889), the functional re- 

 lationship between the thyroid and the pituitary has been 

 intermittently investigated. Up to a decade ago the most 

 convincing experiments had been performed in cold-blooded 

 animals. Among the earliest of such experiments were those 

 reported by Adler in 1914. Only more recently has the un- 

 questionable importance of the anterior pituitary as a regula- 

 tor of thyroid activity been demonstrated in birds and 

 mammals. 



The thyroid-pituitary interrelationship in amphibia. — The 

 discovery of Gudernatsch (1912) that the metamorphosis of 

 the tadpole could be markedly accelerated by the administra- 

 tion of thyroid gland provided a new method for the study 

 not only of metamorphosis but also of the physiology of the 

 thyroid. Two years later Adler was able to prevent meta- 

 morphosis and to cause thyroid atrophy by destroying the 

 hypophysis in tadpoles. All subsequent experiments with the 

 larvae of urodele and anuran amphibia' (salamander, newt, 



• Black (1934) found that, as a result of the injection of a pituitary extract with 

 thyrotropic effects, the oxygen consumption, carbon dioxide production, and 

 nitrogen excretion were all increased in catfish. He concluded that these effects 

 were due to a substance secreted or excreted into the water inasmuch as (i) the 

 effects were not observed in fish kept in flowing water, and (2) the effects were also 

 observed in non-injected fish placed in water in which injected fish had been kept. 



Snakes {Thamnophis sistalis, T. radix) shed repeatedly after hypophysectomy. 

 This effect is prevented by feeding thyroid (Schaefer, 1933). Either hypophysect- 

 omy or thyroidectomy lengthens the molting cycle in another reptile, Hemidactylus 

 brookii (Noble and Bradley, 1933). However, the cycle can be shortened to normal 

 by thyroid treatment. 



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