418 



CELLS, TISSUES, AND ORGANISMS 



^-ANOROSTENEDIONE 



19 -OH-A*-ANDROSTENEDK)NE 



ESTRONE ESTRAOtOL- 17 >9 



Figure 5. Estrogen biosynthesis. 



tween 19-hydroxy-A^-androstenedione and the estrogens may be Hmit- 

 ing; again, inhibitors or accelerators of specific enzymatic steps may 

 be the age-determined factors. 



The increased rate of conversion of estrone and/or estradiol to 

 estriol in older subjects is a most interesting phenomenon. Neither 

 where this may take place in the body nor how it may be accomplished 

 biochemically is at all apparent from presently available evidence. It 

 is notable, however, that a decreased output of estrone and estradiol 

 has been found to occur in men with myocardial infarcts, but a sus- 

 tainment (or slight increase) of estriol excretion occurs. Furthermore, 

 among the Bantu, whose men are characterized by low blood-choleste- 

 rol values and an almost complete absence of myocardial infarction, 

 the total estrogen output, and especially the excretion of estrone and 

 estradiol, is higher than among Europeans of the same age (Bersohn 

 and Oelofse, 1958). Finally, it was found that after estradiol-17/? ad- 

 ministration men with recent myocardial infarction converted it in 

 excess to estriol (Bauld et oL, 1957). Is the relative excess of estriol in 

 older men related to the atherosclerotic process? Does estriol itself have 

 an effect on the process, or is its predominance indicative of some more 

 deep-seated metabolic disturbance? 



In reviewing what findings are available on age relationships in 

 steroid biosynthesis and metabolism, we have also exposed large areas 

 of ignorance. Many details of the chemical transformations undergone 

 in vivo remain to be established. Furthermore, in manv instances 



