PARATHYROID GLANDS 579 



Tetany is especially common at certain seasons of the year, especially 

 in the late winter and early spring. Thus, in places in which the dis- 

 ease is endemic, it often becomes epidemic during the so-called, "tetany 

 months" (March and April). 



The occurrence of the syndrome of tetany appears, in many cases at 

 least, to stand in a definite relation to abolition of, or to insufficiency of, 

 the functions of the parathyroid glands. Thus, it has been shown that, 

 if the parathyroid glands be removed in animals, the operation is followed 

 by the development of a severe, indeed a fatal, form of tetany (tetania 

 parathyropriva) . It has been demonstrated also that the tetany that 

 follows strumectomy in human beings is due to removal of, or injury to, 

 the parathyroid glands; in other words, tetania strumipriva is a tetania 

 parathyropriva. And it is now believed by many, though by no means 

 by all students of the subject, that the syndrome of tetany in all its forms, 

 and whether occurring in children or in adults, is always due to loss of 

 function, or at least to diminution of function, of the parathyroid glands. 

 Though this unitary conception of the pathogenesis of tetany is probably 

 true for several forms, it must be admitted that the definite proof of it 

 has not yet been brought for certain of the forms of tetany. 



Why the nervous system should become more excitable when the para- 

 thyroid function is deficient is not yet known, though it has been thought 

 probable that, during hypoparathyroidism, some chemical substance 

 (hypothetical tetany toxin) that is poisonous to the nervous system de- 

 velops, or is permitted to accumulate, or remains unneutralized, in the 

 body, and that the tetany syndrome is due to intoxication by this sub- 

 stance. 



Interesting studies of intermediary and end metabolism,, in patients 

 suffering from tetany and in animals in which tetany has been produced 

 experimentally, are now being prosecuted in the hope that further clews to 

 the etiology and pathogenesis of the disorder may be discovered. The 

 demonstrations of the occurrence in tetany (1) of disturbances of the 

 acid-base equilibrium (acidosis; alkalosis), (2) of deficiency of sedative 

 ions (calcium and magnesium) and of excess of irritating ions (potas- 

 sium and sodium) in the tissues, and (3) of the excretion of guanidin 

 and guanidin derivatives in the urine, are all interesting in this connec- 

 tion, as are (4) certain experiments bearing upon the ferments produced 

 by the parathyroid glands, (5) those dealing with the relations of thymus 

 function to parathyroid function, (6) those revealing that tetany can be 

 produced by forced respiration, and (7) those concerned with the influence 

 of diet, of occupation and of environment, upon the occurrence of tetany. 



The treatment of tetany is as yet unsatisfactory. With our newer 

 knowledge, however, much can be done to prevent the occurrence of tetany, 

 and researches by both medical and surgical methods, actively carried 

 on, have resulted in the discovery of several helpful therapeutic measures. 



