560 



PHYSIOLOGY OF GONADS 



ously whereas in the cervix and vagina the 

 growth -stimulating action of estrogen is 

 inhibited by progesterone (Fig. 9.1C). This 

 presents a most interesting situation in 

 which the combined actions of two hor- 

 mones on three closely associated structures 

 of the reproductive tract join in a syner- 

 gistic effort in promoting the growth of the 

 uterus although progesterone prevents es- 

 trogen from affecting growth of the cervix 

 and vagina. 



These changes in gross morphology in 

 response to the ovarian hormones are re- 

 flected in the histology of the responding 

 tissues. Also, the character of the response 

 differs depending upon the physiologic na- 

 ture of the tissue concerned; therefore, for 

 the sake of clarity each will be discussed 

 separately. The first of these to be consid- 

 ered is the uterus and particularly growth 

 of the endometrium. 



It has been reported (Hisaw, 1935, 1950) 

 that growth of the endometrium, as induced 

 by estrogen, is limited. That is, a dosage of 

 estrogen capable of maintaining the endo- 

 metrium of a castrated animal for an in- 

 definite period without the occurrence of 

 bleeding, stimulates rapid growth for ap- 

 proximately the first 2 weeks. Within this 

 time a maximal thickness of the endome- 

 trium is attained which remains constant or 

 may become less during the course of treat- 

 ment (Fig. 9.2). Engle and Smith (1935) 

 made similar observations. They found that 

 the endometria of castrated monkeys re- 

 ceiving estrogen for 100 days or longer were 

 thinner than endometria of animals on es- 

 trogen for a much shorter time. Also, on 

 prolonged treatment, the stroma of the en- 

 dometrium becomes dense and the lumen 

 small whereas the size of the uterus remains 

 about the same. In fact, they state that in 



I'll,. (1.2. I'll n Ml lour i-a.-^tra(c>d monkeys wliicli were givi^i 10 /ug. estradiol daily for 10 

 to 78 days. A was given estrogen for 10 days, B for 30 days, C for 60 days, and D for 78 

 days. Depression in the endometrium of anterior wall of D is the result of a biopsy taken 

 a year previously. (From F. L. Hisaw, in A Si/niposium on Steroid Hormones, University 

 of Wisconsin Press, 1950.) 



