THE ADRENAL GLAND 2/9 



by a decrease in the blood level of cortical hormone or some other un- 

 known changes in the composition of the blood traversing the gland. 



(d) The release of epinephrine, which occurs in so many circum- 

 stances, increases adrenal cortical secretion. It may do so either (i) 

 by a direct effect on the gland (which is Vogt's view), (2) by stimula- 

 tion of the anterior pituitary, or (3) as a result of its own effects on the 

 composition of the blood passing through the pituitary. 



The series of events just outlined is a good example of the correla- 

 tion and interplay of three components of the endocrine system, anterior 

 pituitary, adrenal cortex, and medulla. Their combined operation facili- 

 tates the adaptation of the organism to external and internal stresses, 

 stresses which if unchecked would threaten its continued existence. 

 Their operation not only corrects changes in the fluid environment that 

 are detrimental to cellular function but also creates conditions within 

 the environment and the cells that are best adapted to meet the emer- 

 gency. 



Mechanism of Action of Adrenal Cortical 



Hormones 



I would now like to turn from a consideration of the regulation of 

 adrenal cortical activity to the equally complicated question of the man- 

 ner in which the hormones of this gland produce the observed metabolic 

 changes in the cells and body fluids. For it must be in their capacity to 

 facilitate certain types of cellular activity that the protective properties 

 of these hormones reside. 



There is not space here to review the large amount of work that has 

 been done on the function of the cortical hormones. I can but remind 

 you that these hormones are particularly active in the regulation of 

 many phases of metabolism. Thus they regulate the sodium, potassium, 

 and water balance by their influence on the rate of kidney tubular excre- 

 tion and reabsorption of these ions, and in this way they control the 

 shift of fluid and electrolytes between the various compartments of the 

 body. As is now well known, these hormones also have a marked effect 

 on several phases of the organic metabolism. It was recognized many 

 years ago that a subnormal blood glucose level is a frequent finding in 

 adrenal insufficiency in animals and man. Britton has shown that the 

 other carbohydrate constituents of the body, notably the liver and 

 muscle glycogen, are depleted and that the injection of the cortical hor- 

 mone, even without food, rapidly restores these levels. 



