756 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



and (2) similar symptoms to those exhibited by the clinical conditions 

 can be produced experimentally by the removal of the gland in animals. 

 By observations on the effect of administration of thyroid extract to 

 cretinous or myxedematous patients, prompt amelioration of the symp- 

 toms occurs, which certainly suggests that the real cause is the absence 

 of an internal secretion. There is probably nothing more striking in 

 the whole domain of therapeutics than this effect from the administration 

 of thyroid extract or, more so still, of alpha-iodine.* If the treatment is 

 started early enough, the cretinous child from being an ill-developed 

 idiot quickly catches up with children of his own age and becomes in 

 every respect normal. Even if this treatment is not undertaken until 

 the child is several years of age, it is remarkable how quickly the benefit 

 may show itself. In myxedema and cachexia strumipriva also, the 

 symptoms very quickly disappear and the person becomes perfectly nor- 

 mal by the treatment. In all these conditions, however, the thyroid 

 extract must be administered continuously in order to prevent the reap- 

 pearance of symptoms. 



Quite distinct from the above described conditions of hypothyroidism 

 are those produced by an excess of thyroid autacoid in the blood, namely, 

 hyperthyroidism. Such a condition can be produced experimentally in 

 normal animals by. the administration of thyroid extract or alpha-iodine 

 (Kendall). In man large doses are soon followed by great quickening 

 of the pulse with some irregularity, flushing of the skin, increased per- 

 spiration, tremor in the limbs, emaciation, and marked nervous excita- 

 bility. Along with these symptoms, metabolic investigations have shown 

 that the energy output per square meter of surface is greatly increased, 

 being sometimes nearly doubled; that the nitrogen excretion is exces- 

 sive; and that alimentary glycosuria is very commonly present. The 

 body temperature is not, however, as a rule increased, because although 

 metabolism is excited, yet heat loss is correspondingly increased. Ex- 

 ophthalmos is said to develop very occasionally after such administra- 

 tion, but this is doubtful. Lastly, there are usually digestive disturb- 

 ances, although the appetite is likely to be increased. The pulse is quick- 

 ened after administration of alpha-iodine only when protein food is also 

 taken. This is believed by Kendall to be due to the association between 

 the thyroid hormone and the metabolism of the amino acids. 



The symptoms following the injection of the extract are very similar 

 to those of the disease known as exophthalmic goiter. Indeed, the symp- 

 toms are so much alike in the two conditions that it is scarcely neces- 

 sary to describe them specially for the disease except to mention that 

 the exophthalmos is much more likely to be present. 



Like simple goiter this variety is from three to four times more fre- 



* Alpha-iodine refers to the active principle isolated by Kendall. 



