THE AGE FACTOR IN SOME PRENATAL 

 ENDOCRINE EVENTS 



Alfred Jost 



Laboratoire de Biologie animale, P. C. B. 

 Faculte des Sciences, Universite de Paris 



It is evident that age is an essential factor in the study of 

 the foetal endocrine correlations, since the endocrines cannot 

 be expected to play any physiological part before they reach 

 an adequate stage of differentiation. However, physiological 

 specialization does not necessarily parallel morphological 

 organogenesis. A priori three points of view about the foetal 

 endocrine glands may be considered and were effectively sus- 

 tained: 1) the endocrines have no physiological importance at 

 all for the developing foetus; such a view is now difficult to 

 maintain, at least for some glands ; 2) they progressively acquire 

 a state of physiological activity which enables them to work 

 immediately at birth; this interpretation often, and more or 

 less implicitly, involves a similarity between prenatal and post- 

 natal endocrine processes; 3) finally, one may assume that 

 foetal endocrinology implies characteristic events occurring 

 at certain stages of foetal life, and which can be distinct from 

 postnatal function, even if they prepare postnatal life. 



In connection with this last view it should be recalled that 

 some organs pass through a limited phase of sensitivity to 

 hormones. For instance, masculinization of the female uro- 

 genital sinus by testosterone can be produced only during a 

 limited period of time (Turner, 1940; Moore, 1945). Moreover, 

 hormonal treatments may become teratogenic if applied at 

 certain stages: pitressin injected into the rat foetus produces 

 haemorrhages, necrosis and, finally, congenital amputations 

 of the extremities when administered before day nineteen and 

 not afterwards (Jost, 1953c). In recent unpublished observa- 

 tions, I noticed that cortisone injected into the abdominal 

 cavity of rat foetuses (1-3 mg. per foetus) produced cleft 



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