984 



SPERM, OVA, AND PREGNANCY 



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MAXIMUM TITER 



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20 60 100 140 180 ZZO 260 



DURATION OF PREGNANCY DAYS AFTER THE LAST MENSES 



Fig. 16.21. Concentration of human chorionic gonadotiophin in the blood of the normal 

 pregnant woman. The hormone levels were determineti b>' the male frog test. (From A. L. 

 Haskins and A. I. Sherman. J. CUn. Endocrinol., 12, 385, 1952.) 



and concentration of the hormone in the 

 serum is still a matter of conjecture. Browne, 

 Henry and Venning (1938) suggested that 

 the peak level of chorionic gonadotrophin in 

 the blood reflects an increased production 

 and a physiologic need in order to maintain 

 a functional corpus luteum during early 

 pregnancy. Recent evidence has tended to 

 confirm this opinion in that HCG has been 

 found to be active in the maintenance of the 

 secretory activity of the corjius luteum in 

 the primate (Hisaw, 1944; Brown and Brad- 

 bury, 1947; Bryans, 1951 j. In addition, his- 

 tologic studies reveal a direct proportion be- 

 tween the number of Langhans' cells and the 

 amount of hormone excreted (Stewart, Sano 

 and Montgomery, 1948; Wislocki, Dempsey 

 and Fawcett, 1948) . 



The possibility that the kidney plays a 



role in the changes in the concentration of 

 HCG was investigated by Gastineau, Albert 

 and Randall (1948) . The renal clearance was 

 relatively constant throughout all stages of 

 pregnancy although the urine and serum 

 concentrations of the hormone varied as 

 much as 20- fold. In addition, the mean, renal 

 clearance found during pregnancy was not 

 markedly different from that found in cases 

 of hydatiform mole and testicular chorioma. 

 Inasmuch as the renal elimination of the 

 hormone remained constant, it was obvious 

 that two possible explanations existed : these 

 were (1) changes in the secretion rate, and 

 (2) changes in extrarenal disposal of the 

 hormone. Studies on the latter were con- 

 tradictory. Whereas Friedman and Wein- 

 stein (1937) and Bradbury and Brown 

 (1949) reported an excretion of 20 per cent 



