GESTATION 



983 



MAX CONJCENTRATION 

 CONTROP HORMONE 



lOOr n ,'-— X 



WOMAN 



MARE 



10 20 30 40 50 



7. OF DURATION OF PREGNANCY 



60 



70 



80 



90 



100 



Fig. 16.20. The relative time of appearance of placental gonadotropliins in the pregnant 

 mare and the woman. (From E. T. Engle, in Sex and Internal Secretions, 2nd ed., The 

 Williams & Wilkins Company, Baltimore, 1939.) 



pearance of the placental gonadotrophins in 

 the blood and urine of horse and man occurs 

 at approximately the same relative time in 

 pregnancy (Fig. 16.20). The role played by 

 these hormones in gestation is still not clear, 

 but it is significant that their appearance 

 corresponds with the time of implantation 

 of the blastocyst and their disappearance 

 roughly with the time when ovariectomy no 

 longer interferes with the maintenance of the 

 pregnancy. 



/. Human Chorionic Gonndotrophin (HCG) 



The discovery of the presence of a gonado- 

 trophic hormone in human pregnancy urine 

 by Aschheim and Zondek (1927j was soon 

 followed by a description of its biologic ac- 

 tivity and quantitative determinations of 

 its concentration in the urine throughout 

 pregnancy (Ascheim and Zondek, 1928). 

 Recently a number of investigators have de- 

 termined the titer of chorionic gonadotro- 

 phin in the serum of pregnant women. These 

 curves agree very well with the values ob- 



tained from the urine. Figure 16.21 is a typi- 

 cal curve for the concentration of chorionic 

 gonadotrophin in the blood of pregnant 

 women (Haskins and Sherman, 1952). A 

 peak value of 120 I.U. per ml. of serum was 

 obtained on the 62nd day after the last 

 menses and a rapid decline was noted to a 

 low of approximately 10 I.U. per ml. of se- 

 rum on day 154. A subsequent rise to 20 

 I.U. was noted by day 200 and this was 

 maintained until the end of pregnancy. 

 These results are in excellent argeement with 

 those reported by Wilson, Albert and Ran- 

 dall (1949) using the ovarian hyperemia 

 test in the immature rat. These authors ob- 

 tained a peak concentration of approxi- 

 mately 70 I.U. per ml. of serum on the 55th 

 day after the last menses. A gradual decrease 

 occurred thereafter to a low of approxi- 

 mately 20 I.U. per ml. of serum which re- 

 mained unchanged from day 100 to par- 

 turition although the data indicate a slight 

 rise towards the end of pregnancy. 



The significance of the excretion pattern 



