414 CELLS, TISSUES, AND ORGANISMS 



TABLE V 



Rank Ordering of Subjects 

 According to Relative Proportion of THE in the a-Ketol Mixture 



11-dehydrogenation with advancing age is emphasized. There is some 

 suggestion in these data that the relative amount of 5a reduction in- 

 creases in older subjects (the mean percentage of ATHF in the 30 

 young subjects is 17.5 and in the older subjects is 22), a tendency 

 already noted for the ll-oxy-17-ketosteroids (Table III), which are 

 also catabolites of 11-oxygenated corticosteroid precursors. 



Let us now recapitulate the present indications concerning age- 

 related biosynthesis and subsequent metabolism of the three major 

 types of steroid hormone thus far studied in man. These are summa- 

 rized in Table VL 



The degree of sustainment of adrenocortical biosynthesis on into 

 the later decades of life is a notable phenomenon. In this connection I 

 should like to quote Samuels' remarks concerning his studies of 17- 

 hydroxycorticosteroid blood levels in persons of various ages: "One of 

 the striking phenomena brought out by a study of the levels of 17- 

 hydroxycorticosteroids throughout life is the relative constancy from 

 birth to death in the concentrations maintained in the circulating fluids 

 as long as marked pathology does not intervene" (Samuels, 1956). This 

 sustainment of biosynthesis means that the remarkable series of intra- 

 adrenal transformations leading to Cortisol production (Figure 2) are 

 age-independent, and that adequate enzymatic machinery for their 

 accomplishment is maintained. Furthermore, neither acute stress nor 

 exogenous ACTH diminishes the capacity for increased Cortisol pro- 

 duction by this system (Pincus, 1950) in elderly men. We have not 

 conducted any observations in older subjects on the cortisol-secretion 

 response to chronic stress or chronic ACTH administration, although 



