2. Endocrines and Populations 241 



the mobilization and utilization of glucose is inevitably going to have an 

 important bearing on the adaptive responses when a more or less final 

 picture is available of the entire scheme of responses. The frequency of 

 diabetes in, and its effect on, natural populations is unknown, although 

 recent work indicates that under certain circumstances it is far from being a 

 rare disease. 



2. Posterior Pituitary 



The posterior pituitary, or neurohypophysis, has been mentioned re- 

 peatedly in the discussions on the regulation of the secretion of the hor- 

 mones of the anterior pituitary, but in addition the posterior pituitary has 

 important functions of its own in physiologic adaptation. A lengthy discus- 

 sion will not be indulged here, as these functions more properly come under 

 the purview of discussions elsewhere or are insufficiently well known to 

 warrant elaboration in detail. 



a. Antidiuretic hormone. The posterior pituitary secretes an antidiuretic 

 factor (ADH) which is important in regulating the reabsorption of water 

 from the renal tubules. Section of the pituitary stalk with a resultant 

 denervation of the posterior pituitary is followed by diabetes insipidus as a 

 result of the lack of antidiuretic hormone. ADH is apparently manufac- 

 tured in the hypothalamus and traverses the fibers of the supraopticohy- 

 pophyseal tract and is released into the systemic circulation in the posterior 

 pituitary. A vasopressor activity is associated with the antidiuretic factor 

 of the pituitary, but the neurohypophyseal hormone is much less effective 

 in this activity than in its antidiuretic action. There is evidence that the 

 secretion of ADH is increased in response to alarming stimuli as well as to 

 dehydration, but there is also evidence that its secretion is independent of 

 the release of ACTH from the anterior pituitary (cf . above) . For a more 

 detailed account of the pituitary antidiuretic hormone, the reader is re- 

 ferred to the recent review by Thorn ( 1958) . 



h. Lipid mobilizing factor. The recent work of Seifter and his colleagues 

 ( 1959) has indicated the existence of a posterior pituitary lipid-mobilizing 

 factor (LMF) which is released in response to adrenal corticoids. The 

 hormone appears to be a peptide capable of mobilizing triglycerides from 

 the mesenteric fat depots following injections of cortisone, exposure to cold, 

 or subjection to other stimuli which induce an increased adrenocortical 

 secretion. The lipid mobilization is blocked by adrenalectomy or hy- 

 pophysectomy. The pathway for lipid mobilization by LMF in response to 

 alarming stimuli appears to be anterior pituitary, adrenal cortex, and 

 posterior pituitary (Seifter et al., 1959). 



