B. A. HOUSSAY 



epithelium is due to the induecd hypersecretion of the ovarial hormones. 

 To be active, certain hormones require a previous sensitization 

 of the receptor organ by other hormones. Thus, estradiol does not 

 produce hyperplasia of the adrenals in hypophysectomized rats, but 

 this eflfect is produced if the atrophy of the adrenals is prevented by 

 administration of two daily doses of anterohypophysis (Pinto). 

 Chorionic gonadotropin does not induce ovulation in hypophysec- 

 tomized rats, but does so if either serum gonadotropin or stilbestrol 

 is previously injected. 



Metabolism of the Hormones 



At present we live in a period in which the metabolism of the 

 hormones is being energetically studied. The studies include the 

 investigations of origin, transformation, and elimination of the hor- 

 mones. 



The study of origin includes that of their precursors within the 

 organism or in the diet and that of the place and mechanism of elabora- 

 tion within the endocrine gland. 



It is also interesting to know its absorption, its chemical trans- 

 formations, and the site of these transformations. Thus it is known 

 that the estrogens are destroyed principally in the liver and that 

 thyrotropin is transformed by the thyroid into an inactive compound 

 which can be reactivated at a certain temperature. In some cases the 

 disappearance of the hormone can be quantitatively followed. 



The disappearance of the hormone from the blood has been 

 followed in various cases. The unchanged hormone may be elimi- 

 nated in the urine or, secondarily, in the milk or the bile, but in other 

 cases only the transformation products of the hormone are eliminated 

 through these routes. The urine has the advantage, for purposes of 

 extraction, of being a concentrated ultrafiltrate of the plasma virtually 

 free of protein. Hormones of protein nature may or may not filter 

 through the kidney according to their molecular size. Thus chorionic 

 gonadotropin and thyrotropin are found in the urine, but not so the 

 gonadotropin of the pregnant mare serum. The form in which various 

 steroids with estrogenic, androgenic, or corticoid action are eliminated, 

 as well as the total elimination of the 17-ketosteroids, are being in- 

 tensively studied. In some cases the metabolism of a particular 

 hormone can be traced by the assay of some transformation product, 



204 



