2. Endocrines and Populations 207 



However, there are other metaboHtes in the urine in smaller (juantities 

 which cannot be related specifically to particular adrenocorticoids without 

 radioactive labeling, but these ordinarily are not produced in appreciable 

 ciuantities (Gallagher, 1958). The types and quantities of the metabolites 

 of a particular hormone which appear in the urine usually provide a good 

 index of adrenocortical activity for relatively longer periods of time than 

 can be obtained by the measurement of the corticoids in the plasma, which 

 only reflect the immediate situation (Nelson, 1955). However, the urinary 

 metabolites do not always reflect the actual adrenal secretory pattern, as 

 has been shown for mice (Bradlow et at. 1954; Wilson ct al., 1958) although 

 in many instances this may be surmised with confidence (Dorfman, 1960). 

 In summary it may be said that hydrocortisone or corticosterone and C19 

 weak androgens are the major secretory components of the adrenal fascicu- 

 lata, but that other carbohydrate-active corticoids, sodium-retaining corti- 

 coids, and adrenal androgens are also secreted, although usually not in 

 appreciable quantities. 



It is impossible to make hard and fast statements about the quantitative 

 relationships of the adrenocortical hormones to one another because of a 

 certain degree of inherent variability and because the techniciues for their 

 measurement are not sufficiently refined and certain for such detailed 

 comparisons. A large number of steroids have been isolated from the adre- 

 nals of various species, frequently from perfused glands. Some of these may 

 be biochemical artifacts, but many are probably intermediate products in 

 the biosynthesis of the normal secretory products, or possibly steroids which 

 are secreted only under unusual conditions (Jones, 1957; Bradlow and Gal- 

 lagher, 1957; Gallagher, 1958) . It is not known whether or to what extent, 

 some of these steroids are secreted naturally. The picture is complicated 

 further by the fact that the liver and other tissues metabolize the steroid 

 hormones to new steroids which appear in the circulation and urine and 

 which may have biological activity to varying degree (Gallagher, 1958). 

 Therefore, the specific roles of the various adrenocortical steroids and their 

 metabolites, especially those that appear in very low concentrations, in the 

 economy of the w^hole mammal, and the variations in their secretory pat- 

 terns from species to species and under normal and abnormal circumstances, 

 needs clarification. Some of the discrepancies that appear in the literature 

 regarding the relative amounts of various steroids secreted by the adrenals 

 of a particular species seem to depend on whether the measurements were 

 made in vivo or on perfusates of isolated glands (Bush, 1953; Jones, 1957). 

 It seems evident that appreciably higher proportions of steroids which 

 normally are secreted in low concentrations are found in perfusates than in 

 vivo. However, it suffices for the present to know that the carbohydrate- 

 active corticoids, hydrocortisone and corticosterone, are the major na- 



