Endocrine Physiology Intro Class -

8/15/2019 Endocrine Physiology Intro Class -

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ENDOCRINE PHYSIOLOGYENDOCRINE PHYSIOLOGY

Dr.P.Sn.Raju

Asst Prof , Physiology

Andhra medical college

Endocrine PhysiologyEndocrine Physiology



ENDOCRINE PHYSIOLOGYENDOCRINE PHYSIOLOGY

INTROD !TION INTROD !TION 1. Endocrine Gland2. Hormones3. Hormone receptors4. Chemical structure & synthesis5. Hormone secretion, transport and clearance

6. Feed ac! control". #echanism o$ action



%ody s '(o #a)or *e+ulatory ystems%ody s '(o #a)or *e+ulatory ystems

• The endocrine system is one of the body’s two majorregulatory systems. The other one is the nervoussystem.

•In general, nervous system coordinates rapid,precise responses and is especially important inmediating the body’s interaction with the externalenvironment.

• The endocrine, by contrast, primarily controlsactivities that require duration rather than speed. Itregulates, coordinates, and integrates cellular andorgan function at distance.



-E* /0 & E- /C* -E 'E#-E* /0 & E- /C* -E 'E#

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8/C7' /- /F E- /C* -E G87-8/C7' /- /F E- /C* -E G87-

ORGAN HORMONES

HEART ANP

GIT CCK-PZ,SECRETIN, VIP

KIDNEY ERYTHROPOIETIN, 1,25-DHCC

PINEAL GLAND MELATONIN

SKIN CALCIFEROL(V

it-D3)LIVER IGF-I, II

PLATELET PDGF

LYMPHOCYTES IL



Endocrine GlandsEndocrine Glands

Organs and Tissues of the ndocrine !ystem.



Organs and Tissues of the ndocrine !ystem.

Endocrine GlandsEndocrine Glands



'he Functions o$ Endocrine ystem'he Functions o$ Endocrine ystem". #egulating organic metabolism , $ %O and

electrolyte balance, which are important collectivelyin maintaining a constant internal environment.

%. Inducing adaptive changes to help the body cope up with stressful situations.

&. 'romoting smooth, sequential growth anddevelopment.

(. )ontrolling reproduction.

*. #egulating red blood cell production.

+. long with the autonomic nervous system,controlling and integrating activities of both thecirculatory and digestive systems.



Endocrine Gland ?Endocrine Gland ?

• -land is structure which produces something.• ndocrine -lands might be small but of great

importance.

• Terms ndon / within , 0rinein1 to separate.• )alled as 2uctless glands.• 3ses chemical signals for cell to cell

communication• )oordinates the function of cells• #esponse to an endocrine signal occurs within

minutes to hours



Chemical *e+ulatin+ ystems; /<er<ie(Chemical *e+ulatin+ ystems; /<er<ie(

• 'heromones / 4ehavior altering agents,organism to organism communication.

• $ormones• $ormonein / gree5 term , 6to rouse7

6 to !timulate7• cell to cell communication molecules

• 8ade in gland9s: or cells• Transported by blood• 2istant or local target tissue receptors• ctivates physiological response



'ypes o$ hormones'ypes o$ hormones

• F !"ti#!$%• ndocrine $ormones / Travel through the blood to act at

a site distant from the secreting cell or gland• 'aracrine $ormones / ct on cells near the secreting cell• utocrine $ormones / ct on the secreting cell• ;eurocrine $ormones / !ecreted by neural cells

• neurotransmitters• neurohormones

• C&' i"$%• 'rotein < 'olypeptide• mine 9amino acid derived:• !teroid



Chemical #essen+erChemical #essen+er• The multiple activities of the cells, tissues, and

organs of the body are coordinated by the interplayof several types of chemical messenger systems.

• !everal types of chemical messenger systems

a. Neurotransmitters are released by axonterminals of neurons into the synaptic junctionsand act locally to control nerve cell functions.

xample acetylcholine.

b. Endocrine hormones are released by glands orspeciali=ed cells into the circulating blood andin>uence the function of cells at another locationin the body.



Chemical #essen+erChemical #essen+er

c. Neuroendocrine hormones are secreted by neurons into thecirculating blood and in>uence the function of cells at anotherlocation in the body. xamples oxytocin, vasopressin.

d. Paracrines are secreted by cells into the extracellular >uid andaffect neighboring cells of a different type. xample somatostatinsecreted by delta cells in the pancreas.

e. Autocrines are secreted by cells into the extracellular >uid andaffect the function of the same cells that produced them by bindingto cell surface receptors. xamples somatomedin, some growth

factors. f. Cytokines are peptides secreted by cells into the extracellular >uid

and can function as autocrines, paracrines, or endocrine hormones.xample interleu5ins.



ntercellular Communicationntercellular Communication

Cell Target Cell

Cell

Cell Target Cell

Target Cell Neuron

Hormone

Hormone

Hormone Hormone

Hormone

Hormone

Hormone

Endocrine

Paracrine

Autocrine

Blood

Neuroendocrine

Blood

Interstitial Fluid

Interstitial Fluid



• !ignal )hemicals• 8ade in endocrine cells• Transported via blood• #eceptors on target cells

8on+ istance Communication; EndocrineHormones8on+ istance Communication; EndocrineHormones



-euro hormones-euro hormones



9aracrine and 7utocrine Hormones9aracrine and 7utocrine Hormones

• ?ocal communication• !ignal chemicals

diffuse to target• xample )yto5ines

• utocrine/receptoron same cell

• 'aracrine/neighboring cells



• Peptide & Protein Hormones• Steroid Hormones

• Amine Hormones

Classes of Hormones



Hormones = 7 tructural Classi$icationHormones = 7 tructural Classi$ication



Classes o$ HormonesClasses o$ Hormones

4ased on their solubility in water or lipid

a. @ater1soluble hormones 9hydrophilic: 'olarsubstances 1 peptides and catecholamines.

b. ?ipid1soluble hormones 9lipophilic: ;on 'olar 1

steroid and thyroid hormones.



Hormone *eceptorsHormone *eceptors

The locations for the different types of hormonereceptors are generally the following

$ I! #* #! t&' + * $"' # t&' "'%% ' *$!' Themembrane receptors are speciAc mostly for the protein, peptide, and catecholamine hormones .

I! t&' "'%% ".t#/%$+ The primary receptors forthe different steroid hormones are found mainly in

the cytoplasm." I! t&' "'%% ! "%' + The receptors for the thyroid

hormones are found in the nucleus and are believed to be located in direct association with one or more ofthe chromosomes.



*eceptor locations*eceptor locations

• )ell membrane• ?ipophobic ligand canBt

enter cell• Outer surface receptor• Cast response

• )ytosolic or ;uclear• ?ipophilic ligand enterscell• Often activates gene• !lower response



9lasma Concentration9lasma Concentration

'lasma concentration of a hormone is influenced by

a. $ormone secretion.

b. 'eripheral hormone conversion. xample T( → T& 9more active:.

c. $ormone transport 9bound or unbound to plasma protein:.

d. $ormone inactivation.•. 'eptide hormones are inactivated by hydrolysis of peptide

bondsD or engulfed and degradaded intracellularly.•. )atecholamines are en=ymatically converted into inactive

forms.•. ?ipophilic hormones are inactivated by alteration of the active

portions, and liver adds charged groups to ma5e them watersoluble.

e. $ormone excretion by liver and 5idneys.



Hormone ClearanceHormone Clearance

• $ormone must be turned off when served purpose.• 2efines the quantitative removal of hormone from

plasma•

The bul5 of hormone is cleared by liver and 5idneys• Only a small fraction is removed by target tissue• protein and amine hormones bind to receptors and

are internali=ed and degraded•

!teroid and thyroid hormones are degraded afterhormone1receptor complex binds to nuclearchromatin.

• EEF of excreted hormone is degraded or conjugated by'hase I and 'hase II en=yme systems

#eta olic Clearance *ate >#C*?



#C* /F /#E H/*#/-E#C* /F /#E H/*#/-ET"G% / Time ta5en for half of the dose to be eliminated or metabolised.

Hormone Half-life

Amines 2-3 min

T !roid ormones" T# T3

$% da!s'% ( da!s

Pol!peptides #-#' min

Proteins )(-) ' min

Steroids #-)2' min



o(n *e+ulationo(n *e+ulation

• @hen the plasma concentration ofhormone is chronically elevated, the

total number of target1cell receptorfor hormone is gradually reduced as adirect result of the effect a sustainedelevation of hormone has on thehormone receptors.

• This phenomenon prevents the targetcells from overreacting to a prolongedhigh concentration of hormone.



o(n *e+ulationo(n *e+ulationThis down1regulation of the receptors can occur as a result of

". Inactivation of some of the receptor molecule.%. Inactivation of some of the intracellular protein signaling

molecules.

&. Temporary sequestration of the receptor to the inside of thecell, away from the site of action of hormones that interact

with cell membrane receptors.

(. 2estruction of the receptors by lysosomes after they are

internali=ed.*. 2ecreased production of the receptors.

In each case, receptor down1regulation decreases the targettissue’s responsiveness to the hormone.



Endocrine isordersEndocrine isordersToo Little Hormone Activity Too Much Hormone Activity

• Too little hormone secreted bythe endocrine gland(hyposecretion)*

• Increased removal of the hormonefrom the blood

• Abnormal tissue responsiveness tothe hormone

Lack of target-cells receptorsLack of an enzyme essential tothe target-cell response

• Too much hormone secreted bythe endocrine gland(hypersecretion)*

• educed plasma protein bindingof the hormone (too much free!biologically active hormone)

• "ecreased removal of the

hormone from the blood"ecreased inactivation

"ecreased e#cretion

*$ost common causes of endocrine dysfunction



yner+ism yner+ism

• !ynergism occurs whenthe actions of severalhormones arecomplementary and theircombined effect isgreater than the sum oftheir separate effects.

• xample C!$ andtestosterone are requiredfor maintaining thenormal rate of spermproduction.



9ermissi<eness9ermissi<eness

• @ith permissiveness, onehormone must be present inadequate amounts for the fullexertion of another hormone’seffect.

• In essence, the first hormone, by enhancing a target cell’sresponsiveness to anotherhormone, 6permits7 this otherhormone to exert its full effect.

• xample thyroid hormonesincreases the number ofreceptors for epinephrine.



7nta+onism7nta+onism

• ntagonism occurs whenone hormone causes theloss of another hormone’s

receptors, reducing theeffectiveness of the secondhormone.

• xample progesteroneinhibits uterineresponsiveness to estrogenduring pregnancy, bycausing loss of estrogen

receptors.



Feed ac! 8oopsFeed ac! 8oops

e+ati<e Feed ac! Controls;-e+ati<e Feed ac! Controls;



-e+ati<e Feed ac! Controls;8on+ & hort 8oop *e$le@es-e+ati<e Feed ac! Controls;8on+ & hort 8oop *e$le@es



Endocrine *e$le@ 9ath(ays; /<er<ie(Endocrine *e$le@ 9ath(ays; /<er<ie(



-euroendocrine *e$le@es-euroendocrine *e$le@es

• 8any endocrine control systemsinvolve neuroendocrine reflexes, which include neural as well ashormonal components.

• The purpose of such reflexes is toproduce a sudden increase inhormone secretion in response to aspecific stimulus, frequently astimulus external to the body.

• Cor example is the increasedsecretion of cortisol, the H7stresshormone7, by the adrenal cortexduring a stress response.



9rotein and 9olypeptide Hormones9rotein and 9olypeptide Hormones

Hypothalamus

Anterior pituitary

Posterior pituitary

Thyroid

Pancreas

Liver

Parathyroid

• TRH, GnRH, CRH GHRH, Somatostatin,

• ACTH, TSH, FSH, LH, PRL, GH

• Oxytocin, ADH

• Calcitonin

• Insulin,Glucagon,

Somatostatin

• Somatomedin C (IGF-1)

• PTH

Placenta

Kidney

Heart

G.I. tract

Adipocyte

Adrenal medulla

• HCG, HCS or HPL

• Renin

• ANP

• Gastrin, CCK, Secretin, GIP, Somatostatin

• Leptin

• Norepinephrine,epinephrine

*land+Tissue Hormones *land+Tissue Hormones

9rotein and 9olypeptide Hormones;9rotein and 9olypeptide Hormones;



9rotein and 9olypeptide Hormones;ynthesis and *elease


9rotein and 9olypeptide Hormones;9rotein and 9olypeptide Hormones;



• 4inds to surfacereceptor

• Transduction• !ystem activation

• Open ion channel• n=yme activation

• !econd messengersystems

• 'rotein synthesis

9rotein and 9olypeptide Hormone *eceptors9rotein and 9olypeptide Hormone *eceptors



7mine Hormones7mine Hormones

• 2erived from the amino acid tyrosine

Hypothalamus

Thyroid

Adrenal medulla

• Dopamine

• T 3, T 4

• NE, EPI

*land+Tissue Hormones



7mine Hormone tructure7mine Hormone tructure



teroid Hormonesteroid Hormones

Adrenal Cortex

Testes

Ovaries

Corpus Luteum

Placenta

Kidney

• Cortisol, Aldosterone,Androgens

• Testosterone

• Estrogens, Progesterone



• 1,25-Dihydroxycholecalciferol

*land+Tissue Hormones



teroid Hormones; tructureteroid Hormones; tructure



• re made from cholesterol, are lipophilic < canenter target cell

• re immediately released from cell after

synthesis• Interact with cytoplasmic or nuclear receptors• ctivate 2; for protein synthesis

• re slower acting and have longer half1life thanpeptide hormones

• xamples cortisol, estrogen < testosterone

teroid Hormones; Characteristicsteroid Hormones; Characteristics



teroid Hormones; 7ctionteroid Hormones; 7ction



#echanisms o$ action#echanisms o$ action

!teroid < Thyroid hormone mechanisms



• ndocrine glands throughout body are 5ey tochemical integration and homeostasis

• 'rotein, polypeptide and amine hormones areplasma soluble and target membrane

• !urface receptors transduce signals into cell andactivate via second messengers

ummaryummary



• 8ost steroid and some amine hormones arelipophilic, can pass into cell, bind on cytoplasmicor nuclear receptors and activate 2; for proteinsynthesis

• $ypothalamus, pituitary trophic hormone

pathways coordinate endocrine regulation

ummaryummary



Hormones and Their FunctionsHormones and Their Functions

Endocrine Physiology Intro Class -

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