BODY TISSUES 319 



"master gland" seems to control the activity of most of the other en- 

 docrine organs. 



ANTERIOR LOBE. Reduced activity in the anterior lobe of the pituitary 

 gland leads to dwarfism in young animals, accompanied by retention 

 of infantile characteristics and lack of sexual development. Adminis- 

 tration of extracts of the anterior lobe prevents or alleviates these 

 symptoms. Hyperactivity of a growth hormone in the anterior lobe 

 causes gigantism, a condition in which young mammals tend to grow 

 to gigantic proportions. Such individuals may be quite normal men- 

 tally and physically, although in some cases bone malformations may 

 occur. This condition is evinced by overgrowth in bones of the face, 

 hands, and feet of human beings (acromegaly), in addition to excessive 

 growth of fibrous tissue, resulting in thickened nose, eyelids, and fin- 

 gertips. 



A protein has been isolated from ox pituitary glands which causes 

 growth in hypophysectomized rats. It is without influence on depan- 

 creatized animals imless administered along with insulin. Since in- 

 sulin alone has no such effects, some workers believe that the growth 

 hormone stimulates the synthesis of insulin and that the two hormones 

 combine to exert an inhibiting effect on carbohydrate and protein 

 catabolism, thus making these substances available for growth. 



The anterior lobe possesses a hormone which stimulates growth of 

 the adrenals. The adrenocorticotropic hormone (ACTH), a protein 

 of 20,000 molecular weight, has been isolated from the anterior lobes 

 of a number of animals. It has been used medicinally for the treat- 

 ment of arthritis and rheiuiiatism. Presumably it functions through 

 the increased synthesis of hormones such as compound E (page 316). 

 The normal production of ACTH may be under the control of nor- 

 adrenaline (page 315) and adrenaline. In times of stress the level of 

 the latter hormones increases in the blood, leading to increased syn- 

 thesis or release of the pituitary hormone. 



A thyrotropic hormone which stimulates the release of thyroid 

 hormone has been identified. It is a small protein (10,000 g./mole) 

 which on injection into an animal produces an enlargement of the 

 thyroid gland, a rise in basal metabolism, and other symptoms of an 

 excess of thyroid hormone. 



Other hormones isolated from the anterior lobe of the pituitary in- 

 clude (1) the lactogenic hormone, prolactin, a protein which stimu- 

 lates lactation in mammary glands suitably prepared by gonadal 

 hormones, and (2) several gonadotropic hormones which stimulate 

 follicular development in preparation for ovulation and control the 

 development of the corpus luteum. 



