Age Changes in the Ovary 153 



months old and which showed evidence of gonadal insuffici- 

 ency. Ovarian function could, however, be restored by 

 treatment either with extracts of pregnancy urine or with 

 grafts of anterior pituitary tissue. Hoffman (1931) also 

 restored oestrous cycles in old anoestrous mice by transplants 

 of calf pituitary tissue. It is evident from the illustrations 

 provided by Hoffman that the ovaries of these mice, al- 

 though atrophic, still contained many primordial follicles 

 which could respond to gonadotrophin. 



If these experiments are valid, it would seem that, while 

 the function of the ovary fails before that of the pituitary in 

 women, such is not the case in rodents. This inter-species 

 difference is further shown by work on the development of 

 ovarian tumours in the ageing ovaries of rodents transplanted 

 into the spleen. 



Ageing of the ovary and the development of ovarian 

 tumours 



It is known that tumours develop in ovaries that are 

 autotransplanted to the spleen of spayed rats or mice (Bis- 

 kind and Biskind, 1944). The usual explanation for the 

 development of these tumours is that oestrogen from the 

 grafted ovary passes directly into the portal circulation and 

 is destroyed by the liver before the hormone can inhibit the 

 release of gonadotrophin from the pituitary (Golden and 

 Severinghaus, 1938). The imbalance of hormone production 

 by the pituitary persists and stimulates abnormal growth of 

 the graft. While this is true for the rat it may not be so for 

 the rhesus monkey (Van Wagenen and Gardner, 1950) or 

 guinea pig (Wenner and Hoffman, 1950). 



It has already been mentioned that the level of circulating 

 gonadotrophin in women rises as ovarian function declines at 

 the menopause. If there is any reactive tissue remaining in 

 the ovary, one would expect ovarian tumours to become 

 more common in older women. This expectation is not, 

 however, borne out by the facts and one must therefore 

 assume either that the level of gonadotrophin is not high 



