THE ENDOCRINE SYSTEM 



609 



iodine, may be converted to triiodothyronine, which contains one less 

 atom of iodine and is several times more active than thyroxin. It is 

 not yet clear whether the hormone active at the cellular level is thy- 

 roxin itself, triiodothyronine, or some closely related derivative. 



The first clues as to thyroid function came from observations on 

 human disease in 1874 by the British physician, Sir William Gull, who 

 noted the association of spontaneous decreased function of the thyroid 

 and puffy, dry skin, dry, brittle hair, and mental and physical lassi- 



Table 7. HORMONES AND THEIR EFFECTS 



HORMONE 



SOURCE 



PHYSIOLOGIC EFFECT 



Thyroxin 

 Parathormone 



^ Insulin 



Glucagon 



Epinephrine 

 Norepinephrine 

 Hydrocortisone 



Aldosterone 



Adrenosterone 



Growth hormone 



Thyrotropin 



Adrenocorticotropin 



(ACTH) 

 Follicle-stimulating 

 hormone 

 (FSH) 

 Luteinizing hormone 

 (LH) 



Prolactin 



Oxytocin 



Vasopressin 



Intermedin 



Testosterone 



Estradiol 



Progesterone 



Chorionic gonadotropin 



Relaxin 



Thyroid gland 

 Parathyroid glands 



Beta cells of islets in 

 pancreas 



Alpha cells of islets in 



pancreas 

 .Adrenal medulla 

 Adrenal medulla 

 Adrenal cortex 



Adrenal cortex 



Adrenal cortex 



Anterior lobe of 



pituitary 

 Anterior pituitary 



Anterior pituitary 



Anterior pituitary 



Anterior pituitary 



Anterior pituitary 



Hypothalamus, via 



posterior pituitary 

 Hypothalamus, via 



posterior pituitary 

 Intermediate lobe of 



pituitary 

 Interstitial cells of 



testis 

 Follicle of ovary 



Corpus luteum of 



ovary 

 Placenta 



Ovary and placenta 



Increases basal metabolic rate 



Regulates calcium and phosphorus 

 metabolism 



Decreases blood sugar concentration, in- 

 creases glycogen storage and metabo- 

 lism of glucose 



Stimulates conversion of liver glycogen to 

 blood glucose 



Reinforces action of sympathetic nerves 



Constricts blood vessels 



Stimulates conversion of proteins to carbo- 

 hydrates 



Regulates metabolism of sodium and po- 

 tassium 



Androgen, stimulates development of male 

 characters 



Controls bone growth and general body 

 growth 



Stimulates growth and functional activity 

 of the thyroid 



Stimulates adrenal cortex to produce cor- 

 tical hormones 



Stimulates growth of graafian follicles in 

 female and of seminiferous tubules in 

 male 



Controls production and release of estro- 

 gens and progesterone by ovary and of 

 testosterone by testis 



Stimulates secretion of milk by breast, 

 controls maternal instinct 



Stimulates contraction of uterine muscles 



Stimulates contraction of smooth muscles; 



has antidiuretic action on kidney tubules 

 Stimulates dispersal of pigment in chro- 



matophores 

 Androgen; stimulates development and 



maintenance of male sex characters 

 Estrogen; stimulates development and 



maintenance of female sex characters 

 Acts with estradiol to regulate the estrous 



and menstrual cycles 

 Acts, along with other hormones, in the 



maintenance of pregnancy 

 Relaxes pelvic ligaments 



