570 



PHYSIOLOGY OF GONADS 



Fk;. 9.13. The endometrium shown m .4 is (h;i( from a castraled mdiik.N wlml, l,a,l 

 received 10 /xg- estradiol and 2 mg. progesterone daily for 200 days. In B, jiart of ilie endo- 

 metrium of a snndai animal given the same treatment for 312 days is shown at a higher 

 magnification. The endometrium is almost entirely a modified stroma in which glandular 

 epithelium and coiled arteries are absent. Only vestiges of glands are present in the basal 

 area next to the myometrium. 



One of the most interesting aspects of 

 these observations is that these effects were 

 jiroduced by dosages of estrogen and pro- 

 gesterone that are very probably within the 

 range of normal physiology. From this it 

 appears that although growth of the endo- 

 metrium is greater when the two hormones 

 are given together, due to their synergistic 

 interaction, this does not prevent involu- 

 tionary changes from setting in when the 

 treatment is continued for a period of weeks 

 or months. In fact, greater damage to the 

 endometrium occurs under the simultaneous 

 action of the two hormones than when either 

 is given alone. Also, increasing the dose in- 

 tensifies the damaging action of both estro- 

 gen and progesterone, so much so that very 

 large doses will almost completely destroy 

 the endometrium. 



The myometrium, however, shows a dif- 

 ferent response to these treatments. Estro- 

 gen stimulates myometrial growth, which is 



Fir;. 9.14. Uterus of a castrated monkey which 

 was given 10 ixg. of estradiol and 2 mg. pro- 

 gesterone daily for 307 days at which time the 

 injections of progesterone were stopped and estro- 

 gen continued for 20 days. Bleeding occurred the 

 second day following discontinuance of progester- 

 one. The absence of coiled arteries and the pres- 

 ence of cystic glands and a mesenchymetous stroma 

 characterize the endometrium. 



