Nature of the Parathyroid Autacoid 27 



The Mode of Action and the Nature of the Parathyroid 



Autacoid 



The theory that the parathyroids serve the purpose of destroying 

 poisonous products of metabolism which are elaborated in the main thyroid 

 — apart from its a -priori improbability — has received no support from the 

 results of experiment. If the removal of the parathyroids were to be 

 explained in this manner, simple parathyroidectomy should produce much 

 more acute symptoms than total removal of the whole thyroid and para- 

 thyroid apparatus, but Biedl states that there is no difference in the acute- 

 ness of the symptoms. It is, however, possible that, as already stated, the 

 symptoms of tetany may be produced by the presence in the blood of a 

 special toxin — for which the term tetany toxin has been proposed — and 

 that the parathyroids may have the function of destroying or neutralising 

 such a toxin ; in this case they need possess no power of producing an 

 internal secretion. It has also been suggested that there may occur in 

 tetany an accumulation in the blood of toxic intermediate products of 

 protein metabolism, such as appear when the metabolic functions of the 

 liver are interfered with, and that the parathyroids produce an autacoid 

 of hormonic nature which excites some other organ (e.g. the liver) to 

 complete the metabolism of proteins. But the simplest theory to explain 

 the phenomena is that already suggested, which assumes the production 

 of a chalonic autacoid serving to diminish the excitability of nerve-cells. 

 This hypothetical autacoid — which it must be understood has never been 

 isolated — may provisionally be termed parathyrine. We shall see that 

 there is reason to believe that the thyroid produces an autacoid with an 

 opposite tendency. 



The explanation which is often given of parathyroidectomy, as of 

 extirpation of other endocrine glands, that it produces disturbances of the 

 chemical correlation between the blood and organs affected, is merely 

 another way of stating the problem to be explained. 



The production of a special autacoid which tends to regulate the deposi- 

 tion of calcium in the tissues is not proved, and we must bear in mind 

 that any changes which seriously interfere with general nutrition are 

 especially liable to affect the process of ossification. 



Relation of the Parathyroids with Other Endocrine Organs 



Although some authors believe the parathyroids can functionate vicari- 

 ously for the thyroid, the generally received and most probable opinion 

 seems to be that they are independent in function, or, if anything, antagon- 

 istic. They usually show no enlargement in congenital atrophy of the 

 thyroid, and although certain experiments by Vincent and others have 

 appeared to indicate that there may be enlargement and colloid formation 

 after thyroidectomy, it must be borne in mind that it is by no means 

 difficult for errors to creep in in experiments of this kind. 



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