ESTROGEN AND PROGESTERONE 



573 



Fig. 9.19. Sagittal section of the cervix of a pregnant monkey showing conditions present 

 just previous to parturition on the 154th day of gestation. The dominant features are 

 dilation of the cervical canal and reduction of the cervical lips (shown at the left) and the 

 coUiculi. (From Carnegie Institution, No. C713.) 



Hamilton (1949) made a detailed study 

 of the changes in the cervix of rhesus mon- 

 keys during the menstrual cycle, paying 

 particular attention to alterations that took 

 place in the cells of the surface epithelium 

 of the endocervical canal and the cervical 

 glands. It was found that heights of the 

 cells showed consistent increases and de- 

 creases during the cycle. The peaks came on 

 the 3rd, 13th to 15th, and 22nd days, the 

 greatest of these being the 14th day which 

 is approximately the time of ovulation. It 

 also was observed that, following a peak, 

 secretion was associated with the decline. 



Attention was called b3^ Hamilton to the 

 rather close correlation between the fluctua- 

 tions in height of the cervical epithelium in 

 monkeys and the fluctuations observed by 

 Markee and Berg (1944) in the blood estro- 

 gens of the human menstrual cycle. It was 

 concluded that, if similar changes in estro- 

 gen levels also occur in monkeys, one would 

 be justified in concluding that the increase 

 in cell height in the cervical mucosa was due 

 to the action of estrogen and the sudden pe- 

 riodic drops in blood estrogen caused secre- 

 tion and consequent regression. However, it 

 is not clear how this could account for the 

 abundant secretion of the cervical glands in 



the presence of high levels of estrogen during 

 late pregnancy (Fig. 9.19). 



Much has been learned regarding the 

 physiology of the primate cervix from ex- 

 periments on castrated monkeys. The cervi- 

 cal mucosa is very responsive to estrogen 

 and castration atrophy can be repaired and 

 a normal condition maintained by daily in- 

 jections of small doses. Cervical secretion 

 may become abundant when an estrogen 

 treatment is prolonged and especially if 

 large doses are injected. However, the 

 amount of secretion induced by estrogen 

 never equals that of the last half of preg- 

 nancy, and it usually subsides if the injec- 

 tions are continued for several months. 



Under conditions of chronic treatments 

 with estrogen metaplastic aberrations in- 

 variably appear in the epithelium of the 

 endocervix. This reaction was first reported 

 in monkeys by Overholser and Allen ( 1933, 

 1935) and has been confirmed by many in- 

 vestigators (Engle and Smith, 1935; Hisaw 

 and Lendrum, 1936; Zuckerman, 1937c (. 

 Similar lesions may be found in the cervix 

 uteri of women (Fluhmann, 1954). They 

 seem especially prone to occur under con- 

 ditions characterized by excessive produc- 

 tion of estrogen, such as hyperplasia of the 



