FACTORS INFLUENCING OVULATION AND 

 ATRESIA OF OVARIAN FOLLICLES 



SoMERS H. Sturgis 



The human ovary at birth shows a cortex tightly packed with primordial 

 follicles, and almost no interstitial tissue. We may estimate that there are 

 upwards of five hundred thousand eggs in these newborn ovaries from some- 

 what meager evidence such as the finding of a Swedish investigator who 

 counted four hundred and twenty thousand eggs in the ovaries of a 22-year- 

 old normal girl who died suddenly (1). In the human as in other mammals, 

 generally none are left after the age of sixty. If one ovulation were achieved 

 with regularity every month of life from the age of twelve through fifty, 

 then less than five hundred eggs in such a girl would ever achieve ovulation. 

 By far the vast proportion, therefore, are lost in the process of atresia which 

 begins at birth or before, and continues through to the menopause. The 

 chance, then, that any given egg in the neonatal ovary will achieve ovulation 

 is considerably less than one in a thousand. All the other eggs are wasted as 

 their follicles degenerate, and eventually atrophy to an amorphous hyahnized 

 scar. It is important to emphasize that atresia is the usual life story and course 

 of the primate egg and follicle. It is only the unusual egg that matures in a 

 ripening follicle and goes on to ovulate. 



The study of ovulation control must embrace an understanding not only 

 of the mechanisms behind the dramatic success of the unusual follicle that 

 ovulates, but also of the background and physiologic causes for the much 

 more common process of atresia. This process is going on constantly through 

 the normal cycle in adult ovaries in follicles of various stages of development, 

 but there are distinct waves of atresia related to certain times of the cycle. It 

 is hard not to believe that there must be a functional element significantly 

 added to the activity of the adult ovary by the dozens of follicles undergoing 

 atresia at any given time. The reasons for this will be stated later. It is 

 tempting to hope that the causes for atresia might be sufficiently understood 

 so that one might also heighten or accelerate this phenomenon. If hormonal 

 interactions are involved, these might offer a means for physiologic control 

 of ovulation by some direct action on preovulatory follicles causing all to 

 start dissolution before they reached full maturity. 



The massive wastage of germ cells appears to be a rule of nature. Two 

 results of this loss of follicles in the primate ovary are clearly recognized. In 



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