PHYSIOLOGY OF ANTERIOR HYPOPHYSIS 



241 



I. Introduction 



The elucidation of the major functions of 

 the anterior lobe of the pituitary gland will 

 likely stand as an epic in the scientific 

 achievements of the past half century. The 

 series of discoveries which revealed that 

 this part of the hypophysis exercises direct 

 or indirect control over a wide spectrum of 

 biologic processes opened a new physiologic 

 frontier. In no part of this new territory 

 was understanding to be encompassed more 

 spectacularly than by the revelation that 

 the reproductive processes of the Vertebrata 

 as a whole are mediated by secretions of 

 the pituitary gland. It is intriguing to dwell 

 on the evolutionary emergence of this gland 

 which has so wide a control over the growth 

 and development of both somatic and geni- 

 tal structures of the vertebrate body. That 

 this regulator of so many organs and proc- 

 esses arises embryologically from the lining 

 of the oral cavity and that it bears an an- 

 cient, and perchance functional, relation- 

 ship to the primitive diencephalon is in- 

 triguing. The significance of these matters 

 belongs to the future, but of immediate con- 

 cern are the relationships of the pituitary 

 to sex functions and it is to these that at- 

 tention is addressed in this chai)ter. 



The coverage of literature has mainly 

 been restricted to the period since the last 

 edition of this work. The number of papers 

 published in these years is large in propor- 

 tion to the concomitant advancement of 

 the subject. Owing to interruptions of work 

 in reproductive physiology during World 

 War II tmd-the postwar emphasis on those 

 aspects of pituitary physiology which relate 

 to the adrenal cortex and the thyroid, in- 

 terest in the study of gonadotrophic hor- 

 mones waned. The papers cited, by no means 

 a complete list, are important in one or more 

 of the following respects: a pertinent con- 

 tribution to knowledge, an intelligent cor- 

 relation of significant physiologic data, use- 

 ful theorizing, or a guide to the literature 

 in this and related fields. In several in- 

 stances reference is made to earlier works. 

 These help to bring into perspective current 

 information and thought.^ 



' The following review articles, books and mono- 

 graphs are especially pertinent and valuable : Hi- 

 saw, 1947 ; Evans and Simpson, 1950 : Ershoff, 1952 : 



II. The Hypophyseal Gonadotrophins 



During fetal development and in infancy 

 the gonads normally come under little or no 

 important pituitary hormonal influences; a 

 possible exception has been noted in the 

 rabbit (.lost, 1951). Beyond infancy, how- 

 ever, it is clear that the arousal of gonadal 

 functions, including the slow prepubertal, 

 as well as the more spectacular spurt of 

 pubertal development, is entirely dependent 

 on gonad-stimulating hormones secreted by 

 the anterior lobe of the hypophysis. There 

 has been extensive exploration of the ques- 

 tion as to whether the hypophysis secretes 

 one or more than one gonadotrophin. Al- 

 though there is yet very little, if any, knowl- 

 edge of what the hypophyseal cells actually 

 secrete, there is substantial evidence for the 

 present widely held belief that in the mam- 

 mals, at least, the anterior hypophysis se- 

 cretes three trophic substances which stimu- 

 late and govern gonadal activity. These are: 

 the follicle-stimulating hormone (FSH) ; 

 the luteinizing hormone (LH) or interstitial 

 cell-stimulating hormone (IC8H) ; and pro- 

 lactin or lactogenic hormone, which has 

 luteotrophic properties and has been termed 

 luteotrophin (LTH). 



The chemical evidence for the existence 

 of separate gonadotrophins was reviewed by 

 Li and Evans (1948) and Li (1949). Ex- 

 haustive expositions of the chemistry of the 

 adenoliypophyseal luteotrophin, the first of 

 the gonadotroi:)hins to be isolated, have been 

 provided by White (1949) and by Li (19571. 

 The work on FSH and LH was brought up- 

 to-date in 1955 by Hays and Steelman. The 

 results of 25 years of work in these areas 

 leave no doubt that the various biologic ac- 

 tivities which have been demonstrated in 

 whole anterior lobe tissue can be segregated 

 by chemical fractionation procedures. The 

 fact that these activities are identifiable 

 with separate single protein fractions does 

 not provide evidence that they are in fact 

 secreted in the form of proteins with which 

 the biologic activities have been identified. 

 Furthermore, it is important to realize that 



Nalbandov, 1953a ; Sayers and Brown, 1954 ; Benoit 

 and Assenmacher, 1955 ; Cowie and FoUey, 1955 ; 

 Benson and Cowie, 1957; Burrows, 1949; Parkes, 

 1952, 1956 : Harris, 1955 ; Chester Jones and Eck- 

 stein, 1955: and Pickford and Atz, 1957. 



