GONADS AND THE PITUITARY BODY 



Obviously the question of the number of hormones which can 

 be extracted from the pars glandularis cannot be answered 

 until these have been separated as pure substances. Even 

 after this question will have been settled it will not be known 

 how many hormones extracted from the anterior lobe are 

 separately secreted by the normal gland. 



In the preceding section dealing with the assay of gonado- 

 tropic hormone(s) in the mouse and rat, some of the difficul- 

 ties of assay there discussed are especially significant in the 

 attempted identification of separate gonadotropic hormones. 

 Qualitative and quantitative assays are simultaneously at- 

 tempted in the presence of the following variables: (i) the 

 hormone administered acts upon a structure (the ovary) 

 which is complex both anatomically and physiologically. 

 Many investigators believe that each change, or, more often, 

 physiologically similar groups of changes, depend upon spe- 

 cific gonadotropic hormones. However, about the only ova- 

 rian change which can be reasonably isolated for study is 

 ovulation from fully ripened follicles. (2) In most studies the 

 pituitary of the animal used for assay has been disregarded; 

 and (3) the manner in which the hormone is metabolized 

 after injection appears to be of great importance. A single 

 preparation, depending upon dose, frequency of injections, 

 and altered solubility characteristics (as by the addition of a 

 small amount of zinc sulphate to the dissolved extract) may 

 cause only oestrus, or oestrus and follicle growth, or follicle 

 growth and corpus luteum formation (Maxwell, 1934). 



The most clear-cut experiments suggest that two gonado- 

 tropic hormones — one stimulating follicle growth, the other 

 causing luteinization — can be extracted from the pars glandu- 

 laris. Fevold and Hisaw interpret all the cyclic changes in the 

 adult ovary of the rat, in so far as these changes depend upon 

 the pars glandularis, in terms of follicle-stimulating and lute- 

 inizing gonadotropic hormones. 



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