COORDINATION AND CONTROL: (2) THE ENDOCRINE GLANDS 129 



trols certain functions of the adrenal cortex, notably the production of the hor- 

 mone coitisone, with which it is in reciprocal balance. ACTH stimulates cortisone 

 formation, while cortisone inhibits production of ACTH. 



4. The gonadotrophic hormones affect reproductive processes and sexual charac- 

 teristics. The follicle-stimulating hormone (FSH) causes sexual maturation in both 

 male and female; removal of the anterior pituitary in youth therefore has effects 

 much like those of castration. The interstitial-cell-stimulating hormone 1 (ICSH) 

 stimulates testis and ovary to produce hormones that control the development of 

 secondary sex characters. In the female, FSH and ICSH act reciprocally with the 

 ovarian hormones to cause the phenomena of the menstrual and pregnancy 

 cycles. Luteotrophin (which may be the same as prolactin) plays a part in the preg- 

 nancy cycle. The interaction of the gonadotrophic hormones with those of the 

 gonads is discussed more fully in our account of human reproduction (Chap. XVI). 



5. The lactogenic hormone, prolactin, stimulates milk secretion in the mammary 

 glands after birth of the child; it is also apparently responsible for maternal 

 behavior, to ward the young. 



6. The blood-sugar-raising hormone increases the concentration of sugar in the 

 blood; under ordinary conditions its influence is balanced and counteracted by 

 the effects of insulin from the pancreas. Insulin and BSRH form an antagonistic 

 chemical pair, and together control the level of blood sugar. The mechanism is 

 unknown, but it seems likely that the two hormones in some way control the 

 rate at which the liver liberates sugar into the blood. 



7. The fat-metabolizing hormone controls by its amount the rate at which fats 

 are broken down into fatty acids in body metabolism. 



Hormones of the Posterior Lobe. The posterior lobe of the pituitary produces 

 no trophic hormones, but three metabolic hormones have been obtained from it. 



8. The water-balance (antidiuretic) hormone controls the rate at which water 

 is excreted from the body by the kidneys. Removal of the posterior lobe is fol- 

 lowed by excretion of abnormally large amounts of urine accompanied by extreme 

 thirst. This may be the same hormone as (9). 



9. Oxytocin (also called pitocin) throws the muscular wall of the uterus into 

 strong contractions and appears to have importance in relation to childbirth. 

 It has no known function in the male. 



10. Vasopressin (also called pitressin) causes a rise in blood pressure by con- 

 stricting the walls of arteries and may act also on the smooth muscles of the gut. 

 causing them to contract. 



Thyroid. This gland is situated in the neck, and consists of two lobes con- 

 nected by a thin band of thyroid tissue; it partly encloses the trachea. It produces 

 the hormone thyroxin, which is well known chemically and has a large iodine con- 

 tent. This substance controls the general level of metabolism and has marked 

 effects upon growth. If the thyroid glands are removed from young tadpoles, they 

 never change into frogs, but if they are fed large amounts of thyroid tissue, they 

 metamorphose much earlier than is normal and become fully-formed but minute 

 frogs. Thyroid deficiency in human beings is manifested by various effects. If it 

 occurs in infancy and childhood, it produces cretin dwarfs — stunted individuals 

 characterized by obesity, softness and flabbiness of all tissues, feeble-mindedness, 



1 Formerly called luteinizing hormone (LH). 



