THE GONADOTROPIC HORMONES 



ly been published by Levin and Tyndale (1935), Thomsen 

 and Pedersen-Bjergaard (1935-36), Palmer (1937), and Katz- 

 man (1937). 



The assay of the gonadotropic hormones of the anterior pitui- 

 tary. — The "unit" of a gonadotropic hormone, whether the 

 assay be performed in the immature rat or in some other ani- 

 mal, is a term which remains without precision. Recently a 

 start has been made by the National Institute for Medical 

 Research (Great Britain) to set up provisional standards and 

 to determine from the experience of widely separated investi- 

 gators what methods of assay should be recommended. If 

 standard preparations for assay and standard procedures of 

 performing assays are agreed upon and adopted, units of 

 gonadotropic activity designated by different authors can be 

 evaluated with far more assurance than at present. Assay is 

 affected by many factors, the importance of which varies with 

 the source and nature of the gonadotropic agent. For exam- 

 ple, the frequency of injection and the route of injection may 

 greatly modify the response of the immature rat's ovary to 

 pituitary gonadotropic hormone; however. Bates and Riddle 

 (1936) found this not to be true of the effect of hormone on 

 the pigeon's testis.'''' Other obvious factors are the size (or 

 litter-size)^^ of the immature rat, diet, racial strain, ease with 



^"i Bates, Riddle, and Lahr (1935) stated that the response of the immature 

 dove's testis to gonadotropic extract is not affected by the presence or absence of 

 luteinizing hormone. 



^5 An example of work bearing on this factor is the report of Engle, Crafts, and 

 Zeithamel (1937). The effect of the rat's rate of growth on the age and body-weiglit 

 of vaginal canalization was investigated by comparing groups of individuals from 

 litters of varied size — the rate of growth usually being inversely proportional to 

 litter-size. The results were as follows: 



107] 



