THE PITUITARY BODY 



mammals, can be produced by the injection of lactogenic hor- 

 mone into hypophysectomized birds. The authors mention 

 that the response to this hormone in hypophysectomized rab- 

 bits is a small fraction (about one-eighth) of that in normal 

 rabbits. Other authors agree that the lactogenic hormone, by 

 itself, can neither initiate nor maintain lactation in hypophy- 

 sectomized mammals, although the breasts may appear to 

 be fully prepared for stimulation or continuance of stimula- 

 tion. It appears that the initiation or continuance of lacta- 

 tion requires at least two hormones of the pars glandularis — 

 the lactogenic hormone and the hormone stimulating the 

 adrenal cortex ("corticotropic" hormone). Some authors 

 would further lengthen the list, especially with respect to a 

 separate action of the anterior pituitary on carbohydrate 

 metabolism. The importance of all these factors will be con- 

 sidered after the conditions necessary for breast development 

 prior to lactation have been discussed. 



THE INFLUENCE OF THE ANTERIOR PITUITARY ON THE DEVEL- 

 OPMENT OF THE BREASTS PRIOR TO LACTATION 



Before lactation can occur, there must be suitable develop- 

 ment of the breasts. Such development cannot occur in 

 hypophysectomized animals, probably because of two fac- 

 tors: (i) any favorable influence of the gonad will be pre- 

 vented by the lack of gonadotropic hormone, and (2) the an- 

 terior pituitary appears to secrete a hormone essential for 

 mammary development, even when the latter follows the ad- 

 ministration of an oestrogen. 



The development of the mammary gland in relation to oestro- 

 gens? — In a mammal like the rabbit the repeated injection of 

 an oestrogen such as oestrone may cause a marked develop- 

 ment of the mammary tree, especially of the ducts. The 



3 Debre, Marie, and Bernard (1935) described marked development of the 

 breasts in a girl eight years of age without any other signs of puberty. The develop- 

 ment of the vulva and bones corresponded to the child's age. There had been no 

 uterine bleeding. 



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