HORMONES 



fections, toxins, trauma, various poisons, etc. For example, pituitarec- 

 tomized or adrenalectomized animals show a low resistance to all of 

 these, and also are very sensitive to hypoglycemia and hypotensor 

 agents or to the circumstances which provoke shock or hypothermy. 

 Many of these responses depend upon metabolic phenomena. Some 

 endocrine factors also influence the production of immunity antibodies 

 or anaphylaxis and resistance to some infections. The harmful 

 agents or circumstances (e. g., cold, fatigue, toxins, etc.) all produce 

 similar reactions in a given organism, but the nature of these reac- 

 tions varies in different species. The adrenals are largely responsible 

 for these reactions, which pass through several phases: an initial 

 "alarm reaction" followed by temporary compensation, and finally, 

 decompensation. They have been thoroughly studied by Selye. 



Abnormal internal secretions. There are internal secretions 

 produced under abnormal conditions. Thus, when the arterial hyper- 

 tension is produced because the ischemic kidney produces renin, 

 which acts enzymically upon the hypertensinogen of plasma to 

 form hypertensin, a substance which increases the arterial blood 

 pressure. During arterial hypotension, renin is secreted in the 

 blood; but it has not yet been demonstrated with certainty that there 

 is normally a small secretion of renin. 



Hormones and cancer. In certain cases, hormones enhance 

 the development of tumors. Their role seems to consist more in pro- 

 moting the growth of tumors than in initiating the malignant cellular 

 transformation. The extirpation of glands (hypophysis, adrenals, 

 gonads, etc.) or the injection of hormones may hasten or delay the 

 growth of several types of tumors. Thus, testicular castration and 

 injection of estrogenic hormones retard the development of prostatic 

 cancer, whereas testicular hormone accelerates it. 



Some hormones promote the development of cancer. Thus, 

 mammary cancer is less frequent in males or in castrated females of a 

 strain of rat showing high incidence of this cancer in the adult female. 

 The injection of estrogens (Lacassagne) stimulates growth of the mam- 

 mary gland and produces cancer in many of the males of that strain. 

 In these cases, it is debatable whether the estrogens initiate the cancer 

 or merely promote its development. But recent work has shown that 

 estrogenic induction of mammary cancer frequently is obtained in 

 strains of rat in which the cancer occurs spontaneously only in rare 



