402 THE DUCTLESS GLANDS 



Summarizing the effects of the thyroid upon the other 

 endocrinous organs, we may state that there is some evidence 

 that it stimulates the chromaphil tissue to increased activity. 

 There is clear evidence that subthyroidism causes hypertrophy 

 of the pituitary and this is supposed to indicate some kind of 

 vicarious function. It seems clear that while the thyroid has 

 a marked influence upon general metabolism in the young 

 animal, it has a very special influence upon the development 

 and growth of the reproductive organs. The direct effects of 

 thyroid upon thymus are doubtful. The alleged action of 

 thyroid upon the pancreas can only be proved or disproved 

 when our knowledge of carbohydrate metabolism has con- 

 siderably increased. At present there seems no reason to 

 believe that the effects of thyroid upon such metabolism are 

 wholly or in part due to a direct effect upon the internal 

 secretion of the pancreas. 



B. Interrelationships involving the Pituitary Body 



Action of the Pituitary Body upon the Thyroid 



Some recent writers express their belief that a decided anti- 

 thyroid influence is exerted by the substance ("tethelin" 

 Robertson) secreted by the anterior lobe of the pituitary. 



Superpituitarism (by feeding or injection with pituitary 

 substance) is said to cause thyroid hypertrophy, but this is 

 doubtful. 



Apituitarism or subpituitarism is alleged by Gushing to cause 

 hypertrophy of the thyroid. Exner has confirmed this so far 

 as surgical experience in the human subject is concerned. We 

 have seen that extirpation of the thyroid causes hypertrophy 

 of the pituitary. A possible vicarious activity of the two 

 glands has already been discussed. 



Action of the Pituitary Body upon the Reproductive Organs 



It seems clear that certain cases of infantilism are associated 

 with lesions of the pituitary body. Although there has been 

 some discussion as to whether these defects are due to super- 

 or sub-pituitarism it seems from a consideration of the most 

 recent investigations that they are the result of the latter 

 condition. The usually accepted view is that the pituitary 



