GESTATION 



96/ 



S 2 



.t=^t=^t^ 



■J^ri. 



19 21 23 25 27 



H8 Weeks since start of L.M.P. 



^^ 



29 31 33 35 37 39 41 



Caesarian I2!I5 A.M. 

 Fig. 16.4. Free and bound ge.stagen in the plasma of the pregnant human female. (From 



T. R. Forbes, Endocrinology, 49, 218, 1951.) 



L' 16 ^0 Z4 28 32 36 40 1 



90H 



70 



50| 



30 



3 4 5 



Weeks of Pregnancy 



Days after Delivery 



Fig. 16.5. Concentration of gestagen in the blood plasma and pregnanediol in the 

 uterine of the pregnant human female. Gestagen levels were determined by the Hooker- 

 Forbes test. (From K. Fujii, K. Hoshino, I. Aoki and J. Yao, Bull. Tokyo Med. & Dent. 

 Univ., 3, 225, 1956.) 



as with the other species and the values 

 expressed as activity equivalent to pro- 

 gesterone. The values for the bound action 

 were consistently low and, in general, less 

 than 1 fjig. per ml. plasma (Fig. 16.6). The 

 concentration of the free hormone showed 

 marked variations on the first day or so of 

 pregnancy. Actually a variation from 1 

 fig. per ml. plasma to 8 fig. per ml. plasma 

 was seen on day 0. This type of fluctuation 

 has also been seen in the rabbit and is with- 

 out explanation at the present time. How- 

 ever, such marked variations disappeared 

 by the 4th day of pregnancy and the results 

 became much more consistent. The average 



curve for the concentration of gestagen in 

 the blood of the pregnant mouse showed 

 two peaks, one the 7th to the 9th day and a 

 second the 15th day. The concentration 

 increased from 2 fxg. per ml. plasma the 4th 

 day of gestation to an average of approxi- 

 mately 8 fig. the 7th day. This level was 

 maintained until day 9 and fell thereafter 

 with a second peak occurring on day 15 and 

 an immediate drop on day 16. Thereafter 

 the levels remained low throughout the re- 

 mainder of pregnancy. 



Although it may be assumed that the 

 initial peak in the concentration of the 

 gestagen is due to an increased activity 



