The Endocrine Glands -411 



individual reaches maturity. By this time the 

 capacity for skeletal growth is largely re- 

 stricted to the hands, feet, and facial regions; 

 and if acromegaly persists, the jaws become 

 abnormally long and broad, and the brows 

 enlarge to beetling proportions. Also the 

 bones of the hands and feet become abnor- 

 mally thickened, especially at the joints of 

 the fingers and toes. 



The Gonadotrophs Hormones. Three gonad- 

 stimulating fractions have now been iden- 

 tified. These are called FSH (follicle-stimu- 

 lating hormone), LH (luteinizing hormone), 

 and LT (luteotrophin). All are protein com- 

 pounds, the first two being glycoproteins. 



In males and females, both FSH and LH 

 are necessary, for puberty to be established 

 in younger animals and for the sexual func- 

 tions to be maintained in older individuals. 

 Without FSH, the Graafian follicles fail to 

 develop, or, if the animal is male, the semi- 

 niferous tubules remain inactive. Without 

 LH, on the other hand, ovulation does not 

 occur; that is, the ripe eggs are retained 

 within the follicles, or in male specimens, the 

 interstitial tissue of the testis remains dor- 

 mant and fails to produce testosterone. FSH 

 accordingly serves to stimulate growth in the 

 Graafian follicles and seminiferous tubules, 

 whereas LH induces ovulation and activates 

 the corpus luteum (in the female) and en- 

 hances the activity of the interstitial tissue 

 (in the male). 



The third gonadotrophin of the anterior 

 pituitary, luteotrophin, serves primarily to 

 sustain the corpus luteum during the early 

 part of pregnancy. Luteotrophin also has an 

 important secondary action — on the mam- 

 mary glands. It is responsible for inducing an 

 active secretion of milk. However, luteotro- 

 phin can do this only after the glands have 

 been stimulated previously by estrogen and 

 progesterone— and possibly also by another 

 unidentified pituitary hormone. Formerly it 

 was thought that the luteotrophin and the 

 lactogenic hormone were separate entities, 

 but now it seems evident that they are a 

 single compound. Moreover, this same com- 



pound exerts a distinct influence on maternal 

 behavior, at least in many species. 



Thyrotrophic and Corticotrophic Hormones. 

 The consistent regression of both the thyroid 

 and adrenal cortex in animals deprived of 

 the pituitary soon indicated that probably 

 the pituitary produces two other hormones; 

 and recently thyrotrophin, which is also 

 called the thyroid-stimulating hormone 

 (TSH), and the adrenocorticotrophic hor- 

 mone (ACTH) have been identified. 



The thyroid gland is exceedingly sensitive 

 to stimulation by TSH and, in fact, the pri- 

 mary disturbance in exophthalmic goiter 

 appears to be an overproduction of this hor- 

 mone by the anterior pituitary. 



A triumph of biochemical research was 

 consummated recently with the synthesis in 

 1961 of a very active part of the ACTH mole- 

 cule. This work was done by K. Hofmann 

 and collaborators at the University of Pitts- 

 burgh. A previous analysis of purified ex- 

 tracted hormone had revealed it to be a pep- 

 tide chain, consisting of some 39 amino acid 

 units. However, the part synthesized, in 

 which 23 amino acids are united in proper 

 sequence, displays almost as much activity as 

 the total molecule. Then finally, in 1963, the 

 total synthesis of ACTH was achieved by 

 Schwyzer and Sieber in the Ciba laboratory, 

 Switzerland. 



As the name implies, ACTH stimulates the 

 production or release of the adrenocortical 

 hormones, particularly Cortisol. Like Corti- 

 sol, therefore, ACTH is effective in alleviat- 

 ing the symptoms of a number of diseases, 

 including rheumatoid arthritis, asthma, and 

 allergies generally. A study of ACTH and 

 of the corticosteroids has led to a general 

 theory, called the stress theory, as to the 

 basic nature of the sustained reactions of the 

 body to stress, including particularly the 

 stress imposed by disease-producing agents. 

 As greater quantities of these synthesized 

 hormones become available, it will probably 

 be possible to evaluate their physiological ac- 

 tivity more precisely. Meanwhile, because of 

 their great potency and because of inade- 



