第12章 内分泌系统

第12章内分泌系统与化学调节内分泌系统：由内分泌腺和分散存在于某些组织器官中的内分泌细胞组成的一个体内信息传递系统。激素（hormone）：由内分泌腺或散在内分泌细胞所分泌的高效能的生物活性物质，经组织液或血液传递而发挥其调节作用。激素调节是体液调节的主要形式。内分泌腺与外分泌腺的区别：内分泌腺：无导管，分泌物直接释放入血液。外分泌腺：有导管，分泌物释放入管道。Endocrinesystem:Theendocrinesystemconsistsofanumberofglandslocatedthroughoutthebodythatproduceandsecretesubstancescalledhormonesintotheblood.Ahormoneisachemicalthatinfluencesorcontrolstheactivityofaspecifictissueororgan.Likethenervoussystem,theendocrinesystemcoordinatesthefunctioningofbodyparts.Thenervoussystemisfastactingandutilizesnerveimpulsesthattravelrapidlyalongnervefibers.Theendocrinesystemissloweractingbecauseittakestimetodeliverhormonestotargetorgans,buttheactionofhormonesislongerlasting.EndocrineGlands:Becauseendocrineglandseventuallylosetheirducts,theyareoftencalledductlessglands.Theyproducehormones,regulatorychemicalsthattheysecretedirectlyintotheextracellularspace.Thehormonesenterthebloodorlymphaticfluid.ExocrineGlands:arefarmorenumerousthanendocrineglands,andmanyoftheirproductsarefamiliar.Themulticellularglandssecretetheirproductsthroughaductontobodysurfacesorintobodycavities.Exocrineglandsareadiverselot.Theyincludemucous,sweat,oil,andsalivaryglands,theliver,thepancreas,andmanyothers.本章主要内容一、化学调节的性质二、脊椎动物的化学调节三、激素与稳态

重点:激素的作用特点,两类激素的作用机制，腺垂体、甲状腺、胰岛素、糖皮质激素、肾上腺髓质激素的作用。一、化学调节的性质1、激素的作用2.激素的作用机制激素的作用(actionsofhormone)Hormonesbringabouttheircharacteristiceffectsontargetcellsbyalteringcellactivity;thatis,theyincreaseordecreasetheratesofnormalcellularprocesses.Thepreciseresponseisdictatedbythetargetcelltype.Forexample,epinephrinebindingtosmoothmusclecellsinbloodvesselwallsstimulatesthemtocontract.Epinephrinebindingtocellsotherthanmusclecellsmayhaveadifferenteffect,butitwillnotcausethosenoncontractilecellstoshorten.Ahormonalstimulustypicallyproducesoneormoreofthefollowingchanges:Changesinplasmamembranepermeabilityand/orelectricalstate(membranepotential)byopeningorclosingionchannels.Synthesisofproteinsorcertainregulatorymolecules(suchasenzymes)withinthecell.Enzymeactivationordeactivation.Inductionofsecretoryactivity.Stimulationofmitosis.激素调节的一般特征：

（1）信使作用;

（2）相对特异性;

（3）高效性

;

（4）激素间的相互作用；

（5）激素调节比神经调节慢，但作用持久。(6)激素的分泌有节律性。激素的作用：（1）维持稳态。（2）促进生长发育。（3）促进生殖活动。（4）调节能量转换。（5）调节行为。生长激素

促甲状腺激素

促肾上腺皮质激素促性激素胰高压糖素

胰岛素甲状腺激素睾丸酮、雌激素、孕激素肾上腺皮质激素、糖皮质激素根据激素的化学成分分类：含碘的氨基酸肽和蛋白质类固醇激素作用时间长含氮激素作用迅速2.激素的作用机制Thechemistryofhormones:Hormonesmaybedefinedaschemicalsubstances,secretedbycellsintotheextracellularfluids,thatregulatethemetabolicfunctionofothercellsinthebody.Althoughalargevarietyofhormonesareproduced,nearbyallofthemcanbeclassifiedchemicallyaseitheramino

acid-basedhormonesorsteroids.Mosthormonesbelongtothefirstgroup.Molecularsizevarieswidelyinthisgroup—fromthesimpleaminoacidderivatives,whichincludetheaminesandthyroxinetopeptides(shortchainsofaminoacids),toproteins(longpolymersofaminoacids).Hormonesofthesecondgroup,thesteroids,aresynthesizedfromcholesterol.Ofthehormonesproducedbythemajorendocrineorgans,onlythegonadalhormonesandadrenocorticalhormonesaresteroids

激素受体：指靶细胞上能识别并专一性结合某种激素，继而引起各种生物效应的功能蛋白质。激素受体的分类：

细胞膜受体：G蛋白耦联受体和酪氨酸蛋白激酶受体结构分为膜外区段、质膜部分和膜内区段

细胞内受体：分为胞浆受体和核受体核受体的结构分为激素结合结构域、DNA结合结构域和转录激活结构域

2.1含氮激素的作用机制—第二信使学说

激素(第一信使)与靶细胞上的受激活催化体结合腺苷环化酶ATP（胞内）cAMP酶反应生理活动(第二信使）2.1含氮激素的作用机制—第二信使学说（肾上腺素的作用）作为第一信使的激素在血液中的含量虽然极低，但通过细胞的信号传导途径，微弱的化学信号可以被逐级放大。Aminoacid-basedhormonesandsecond-messengersystems:Becauseproteinsandpeptidescannotpenetratetheplasmamembranesoftissuecells,virtuallyalloftheaminoacid-basedexerttheirsignalingeffectsthroughintracellularsecondmessengersgeneratedbyhormonebindingtoplasmamembranereceptors.Ofthesecondmessengers,cyclicAMP,whichalsomediatestheeffectsofcertainneurotransmitters,isbyfarthebestunderstood,soitwillreceivemostofourattention.Aminoacid-basedhormonesorpeptidehormonesactasmessengersthatstimulatecellsbybindingtospecificreceptorsintheplasmamembrane.ThehormonereceptorcomplexactivatesanenzymethatproducescyclicAMP(cAMP),acompoundderivedfromATP.cAMP,servingasaso-calledsecondmessenger,thenactivatesotherenzymesthatcarryoutvariouscellularactivities.Otherpeptidehormonesutilizecalcium(Ca2+)asasecondmessenger.2.2类固醇激素作用机制—

基因表达学说

类固醇激素进入细胞内，与胞浆靶受体分子结合后，启动了细胞核内相关基因表达。Steroidhormonesanddirectgeneactivation:Beinglipidsoluble,steroidhormone(and,strangely,thyroidhormone,asmalliodinatedamine)candiffuseeasilyintotheirtargetcells.Onceinside,theybindtoanintracellularreceptorthatisactivatedbythecoupling.Theactivatedhormone-receptorcomplexthenmakesitswaytothenuclearchromatin,wherethehormonebindstoaDNA-associatedreceptorproteinspecificforit.Thisinteraction“turnson”agene,thatis,itpromptstranscriptionofDNAtoproduceamessengerRNA(mRNA).ThemRNAisthentranslatedonthecytoplasmicribosomes,producingspecificproteinmolecules.Theseproteinsincludeenzymesthatpromotethemetabolicactivitiesinducedbythatparticularhormoneand,insomecases,synthesisofstructuralproteinsthatareexportedbythetargetcell.

Cellularactivityofhormones:Peptidehormonescombinewithreceptorslocatedontheplasmamembrane.ThispromotestheproductionofcyclicAMPwhich,inturn,leadstoactivationofparticularenzymes.Steroidhormonespassthroughtheplasmamembranetobindwithreceptors;thehormonereceptorcomplexmovesintothenucleusandactivatescertaingenes,leadingtoproteinsynthesis.二、脊椎动物的化学调节1.脊椎动物的内分泌系统2.内分泌系统与神经系统的联系3.垂体的内分泌功能

1.脊椎动物的内分泌系统

内分泌系统：是由内分泌腺

和分散存在于某些组织器官中的内分泌细胞组成的一个信息传递系统。内分泌腺:垂体、甲状腺、甲状旁腺、肾上腺、胰岛、性腺、松果体、胸腺内分泌细胞：消化道粘膜、心、肾、肺、皮肤、胎盘等部位存在各种内分泌细胞兼有内分泌功能的细胞：神经内分泌细胞Comparedtootherorgansofthebody,theorgansoftheendocrinesystemaresmallandunimpressive.Indeed,tocollect1kgofhormone-producingtissue,youwouldneedtocollectalloftheendocrinetissuefromeightornineadults!Inaddition,theanatomicalcontinuitytypicalofmostorgansystemsdoesnotexistbetweentheendocrineorgans.Instead,endocrineorgansarewidelyscatteredaboutthebody.Theendocrineglandsofthebodyincludethepituitary,thyroid,parathyroid,adrenal,pineal,andthymusglands.Inaddition,severalorgansofthebodycontaindiscreteareasofendocrinetissueandproducehormonesaswellasexocrineproducts.Suchorgans,whichincludethepancreasandgonads,arealsomajorendocrineglands.Thehypothalamusalsofallsintothislattercategory.Alongwithitsneuralfunctions,itproducesandreleaseshormones,sowecanconsiderthehypothalamusaneuroendocrineorgan.Besidesthemajorendocrineorgans,variousothertissuesandorgansproducehormones.Forexample,pocketsofhormone-producingcellsarefoundinthewallsofthesmallintestine,stomach,kidneys,andheart—organswhosechieffunctionshavelittletodowithhormoneproduction.These.人体主要内分泌腺2.内分泌系统与神经系统的联系哈里斯的下丘脑调节腺垂体的神经-体液学说:下丘脑腺垂体靶腺体下丘脑是身体内分泌系统的总枢纽，它通过垂体将神经系统与内分泌系统有机地联系起来。

3.垂体的内分泌功能Hypothalamusandthepituitary.Thehypothalamusproducestwohormones,ADHandoxytocin,whicharestoredandsecretedbytheposteriorpituitary.Thehypothalamuscontrolsthesecretionsoftheanteriorpituitary,andtheanteriorpituitarycontrolsthesecretionsofthethyroid,adrenalcortex,andgonads,whicharealsoendocrineglands.

促激素:促肾上腺皮质激素、促甲状腺激素、促卵泡激素、促黄体素、促黑色细胞刺激素腺垂体生长激素(growthhormone,GH)催乳素垂体抗利尿激素（ADH)神经垂体催产素垂体位于脑下部的垂体窝内，借漏斗连于下丘脑。Posteriorpituitary:Theposteriorpituitaryisconnectedtothehypothalamusbymeansofastalklikestructure.Thehormonesreleasedbytheposteriorpituitaryaremadebyneurosecretorycellsinthehypothalamus.Thehormonesthenmigratethroughaxonsthatterminateintheposteriorpituitary.Antidiuretichormone(ADH),alsocalledvasopressin,promotesthereabsorptionofwaterfromthekidneys,therebypreventingdehydration.Thehypothalamusisbelievedtocontaincellsthataresensitivetobloodsoluteconcentrations.Whenthesecellsdetectthatthebloodlackssufficientwater,ADHisproducedbyspecialneurosecretorycellsandistransportedbytheirfiberstotheposteriorpituitary,whereitisreleased.Asthebloodbecomesmoredilute,thehormoneceasestobeproducedandreleased.InabilitytoproduceADHcausesdiabetesinsipidus,inwhichapersonproducescopiousamountsofurinewitharesultantlossofelectrolytesfromtheblood.TheconditioncanbecorrectedbytheadministrationofADH.Oxytocinisanotherhormonemadeinthehypothalamusandreleasedbytheposteriorpituitary.Oxytocincausestheuterustocontractandcanbeusedtoartificiallyinducelabor.Italsostimulatesthereleaseofmilkfromthebreastwhenababyisnursing.下丘脑通过分泌释放激素或释放抑制激素来控制脑垂体前叶（腺垂体）的活动。促甲状腺素释放激素（TRH）：为3肽，促进TSH和PRL分泌。促肾上腺皮质激素释放激素（CRH）：多肽，促进ACTH分泌卵泡刺激素释放激素（FRH):10肽，促进FSH分泌黄体生成素释放激素（LRH）：10肽，促进LH分泌生长素释放激素（GRH）：10肽，促进GH分泌生长素释放抑制激素（GRIH)：14肽，抑制GH及TSH的分泌催乳素释放激素（PRH）：促进催乳素分泌催乳素释放抑制激素（PRIH）：抑制催乳素分泌促黑激素释放激素（MRH）：5肽，促进MSH分泌促黑激素释放抑制因子（MRIH）：3肽，抑制MSH分泌

生长激素蛋白质合成骨的生长生长发育促进代谢甲状腺激素性激素雌激素雄激素孕激素促甲状腺激素释放激素甲状腺生长激素释放因子下丘脑(内分泌活动的调节中枢)促甲状腺激素垂体促性腺激素释放激素促性腺激素睾丸或卵巢生殖器官第二性征子宫内膜和乳腺Anteriorpituitary:Thehypothalamuscontrolstheanteriorpituitarybyproducinghypothalamic-releasingandrelease-inhibitinghormones,whicharetransportedtotheanteriorpituitarybythebloodwithinaportalsystem.Eachofthesehypothalamichormonescausestheanteriorpituitaryeithertosecreteortostopsecretingaspecifichormone.Theanteriorpituitaryproducesseveraldifferenthormonesasfollowedfigure.Negativefeedbackintheregulationofthehypothalamus,anteriorpituitary,andthyroid.a.thelevelofthyroid-stimulatinghormones(TSH)exertsfeedbackcontroloverthehypothalamus.b.thelevelofthyroxineexertsfeedbackcontrolovertheanteriorpituitary.c.thelevelofthyroxineexertsfeedbackcontroloverthehypothalamus.Inthisway,thyroxinecontrolsitsownsecretion.Cortisolandsexhormonelevelsarecontrolledinsimilarways.促激素的功能：维持相关腺体的正常发育促进相关腺体内激素合成和分泌生长激素的功能：蛋白质合成和骨的生长。催乳素：促进乳汁的合成分泌。生长激素分泌异常侏儒症巨人症16岁的姚德芬身高2.36米，体重180公斤，她的身高是长年罹患垂体瘤导致“巨人症”的结果。

Growthhormone(GH):Growthhormone,orsomatotropin,producedbytheanteriorpituitary,affectsthephysicalappearancedramaticallysinceitdeterminesanindividual’ssizeandheight.IflittleornoGHissecretedbytheanteriorpituitaryduringchildhood,apersoncanbecomeapituitarydwarf,characterizedbyperfectproportionsbutsmallstature.IftoomuchGHissecreted,apersoncanbecomeagiant.Giantsusuallyhavepoorhealth,primarilybecauseGHhasasecondaryeffectonthebloodsugarlevel,promotinganillnesscalleddiabetesmellitus.GHisproducedingreatestquantitiesduringchildhoodandadolescence,whenmostbodygrowthisoccurring,butisstillproduced(thoughinlowerquantities)inadultstoaidincontinuedproteinsynthesisandnormalcelldivisionandreplacement.IfGHproductionincreasesinanadultafterfullheighthasbeenobtained,onlythebonesofthejaw,eyebrowridges,nose,fingers,andtoesrespond.Whenthesebonesbegintogrow,thepersonacquiresaslightlygrotesquelook,withhugefingersandtoes.Thisconditioniscalledacromegaly.Prolactin(PRL):PRLisproducedbytheanteriorpituitaryonlyafterchildbirth.Itcausesthemammaryglandsinthebreasttodevelopandproducemilk.Theanteriorpituitaryalsosecretesthehormonesthatfollow.Sincethesehormoneshaveeffectonotherendocrineglands,theanteriorpituitaryissometimescalledthemastergland.三、激素与稳态1.甲状腺调节发育与代谢2.甲状旁腺维持钙稳定3.胰腺调节血糖水平4.肾上腺髓质动员应急反应5.肾上腺皮质的内分泌是维持生命所必需的6.性腺分泌性激素1.甲状腺调节发育与代谢:位于颈前部喉下部、气管上部的两侧和前面。呈‘H’形，是人体内最大的内分泌腺。甲状腺分泌甲状腺激素。Thethyroidgland:Thebutterfly-shapedthyroidglandislocatedintheanteriorneck,onthetracheajustinferiortothelarynx.Itstwolaterallobesareconnectedbyamediantissuemasscalledtheisthmus.Thethyroidglandisthelargestpureendocrineglandinthebody.Itsprodigiousbloodsupply,makesthyroidsurgeryapainstaking(andbloody)endeavor.Internally,thethyroidglandiscomposedofhollow,sphericalfollicles.Thewallsofeachfollicleareformedlargelybycuboidalorsquamousepithelialcellscalledfolliclecells,whichproducetheglycoproteinthyroglobulin.Thecentralcavity,orlumen,ofthefolliclestorescolloid,anamber-colored,stickymaterialconsistingofthyroglobulinmoleculeswithattachediodineatoms.Thyroidhormoneisderivedfromthisiodinatedthyroglobulin.Theparafollicularcells,anotherpopulationofendocrinecellsfoundinthethyroidgland,producecalcitonin,anentirelydifferenthormone.Theparafollicularcellsliewithinthefollicularepitheliumbutprotrudeintothesoftconnectivetissuethatseparatesandsurroundsthethyroidfollicles.

甲状腺激素的合成与代谢

有两种：T3和T4

合成的原料：碘和酪氨酸合成过程分为三步：

（一）甲状腺腺泡聚碘

聚碘是逆电化学剃度的继发性主动转运

（二）I-的活化

I-在过氧化酶的作用下变成I2或I0

（三）酪氨酸碘化与甲状腺激素的合成

甲状腺球蛋白酪氨酸残基上的氢原子可被碘原子取代或碘化，首先生成一MIT和DIT，然后两DIT耦联T4；一个MIT与一个DIT发生耦联，形成T3

（四）甲状腺激素的贮存、释放、运输与代谢1．贮存：在腺泡腔内以胶质的形式贮存。2．释放：3．运输：以两种形式在血液中运输，一种是与血浆蛋白结合，另一种则呈游离状态。4．代谢：血浆T4半衰期为7天，T3半衰期1.5天。

（二）甲状腺激素的生理作用主要作用是促进物质与能量代谢，促进生长和发育过程，提高产热量。

1.对代谢的影响

a.产热效应：提高组织耗氧率，增加产热量，与Na+-K+-ATP酶有关。甲亢时，产热量增加，基础代谢率升主患者喜凉怕热，极易出汗；功能低下时，产热量减少，基础代谢率降低，患者喜热恶寒。

对蛋白质、糖和脂肪代谢的影响蛋白质：生理剂量促进合成；过多加速分解，导致消瘦；不足，蛋白质合成减少，但组织间的粘蛋白增多，引起粘液性水肿（myxedema）。

糖：提高血糖，促进糖的吸收；增强糖原分解，抑制糖原合成；增强肾上腺素、胰高血糖素、皮质醇和生长素的生糖作用。

脂肪：促进脂肪的分解，对胆固醇以分解为主。

2.对生长与发育的影响

维持正常生长发育不可缺少的激素，

特别是对骨和脑的发育尤为重要。幼年时缺乏患呆小症（cretinism）。甲状腺机能不足发生在成年则引起粘液性水肿。

3.对神经系统的影响

可提高中枢神经系统的兴奋性。甲亢时；注意力不易集中、过敏疑虑多愁善感、喜怒失常、烦躁不安、睡眠不好而且多梦幻，以及肌肉纤颤等。功能低下时：中枢神经系统兴奋性降低，出现记忆力减退，说话和行动迟缓，淡漠无怀与终日思睡状态。

甲状腺激素对心脏有明显兴奋作用。

Thyroidhormone:Thyroidhormone,oftenreferredtoasthebody’smajormetabolichormone,isactuallytwoactiveiodine-containinghormones,thyroxine,orT4,andtriiodothyronine,orT3.thyroxineisthemajorhormonesecretedbythethyroidfollicles;mosttriiodothyronineisformedatthetargettissuesbyconversionofT4toT3.Thesetwohormonesareverymuchalike.Eachisconstructedfromtwothyrosineaminoacidslinkedtogether,butthyroxinehasfourboundiodineatoms,whereastriiodothyroninehasthree.Exceptfortheadultbrain,spleen,testes,uterus,andthethyroidglanditself,thyroidhormoneaffectsvirtuallyeverycellinthebody.Generallyspeaking,itstimulatesenzymesconcernedwithglucoseoxidation.Inthisway,itincreasesbasalmetabolicrateandbodyheatproduction;thisisknownasthehormone’scalorigeniceffect.Thyroidhormonealsoprovokesanincreaseinthenumberofadrenergicreceptorsinbloodvessels,soitplaysanimportantroleinmaintainingbloodpressure.Additionally,itisanimportantregulatoroftissuegrowthanddevelopment;itisspeciallycriticalfornormalskeletalandnervoussystemdevelopmentandmaturationandreproductivecapabilities.甲状腺分泌活动的调节

1.下丘脑-腺垂体对甲状腺的调节2.

甲状腺激素的反馈调节

3.甲状腺的自身调节

甲状腺本身还具有适应碘的供应变化，调节自身对碘的摄取以及合成与释放甲状腺激素的能力；在缺乏TSH或TSH浓度不变的情况下，这种调节仍能发生，称为自身调节。4.自主神经对甲状腺活动的影响

交感兴奋合成增多，胆碱能神经兴奋

合成减少。甲状腺机能的异常1、单纯性甲状腺肿2、甲状腺机能低下（1）.呆小症（2）.黏液性水肿3、甲亢Iodine,whichisrequiredforthyroxineproduction,isactivelytransportedintothethyroidgland,whereitsconcentrationmaybeasmuchas25timesthatfoundintheblood.Ifiodineislackinginthediet,thethyroidglandenlarges,producingasimplegoiter.Theuseofiodizedsalthelpspreventsuchacondition.呆小症（cretinism):Failureofthethyroidtodevelopproperlyresultsinaconditioncalledcretinism.Cretinsareshortandstocky,andhavehadextremehypothyroidismsincechildhoodorinfancy.Thyroxinetherapycaninitiategrowth,butunlesstreatmentisbeginwithinthefirsttwomonthsofbirth,mentalretardationresults.甲状腺功能低下引发的粘液性水肿(myxedema):Hypothyroidisminadultsproducestheconditionknownasmyxedema,whichischaracterizedbylethargy,weightgain,lossofhair,slowerpulserate,loweredbodytemperature,andthicknessandpuffinessoftheskin.Theadministrationofadequatedosesofthyroxinrestoresnormalfunctionandappearance.

Inthecaseofhyperthyroidism,orGraves’disease,thethyroidglandisenlargedandoveractive,causingagoitertoformandtheeyestoprotrudebecauseofedemaineyesockettissuesandswellingofextrinsiceyemuscles.Thistypeofgoiteriscalledexophthalmicgoiter.Thepatientusuallybecomeshyperactive,nervous,andirritable,andsuffersfrominsomnia.Hyperthyroidismcanalsobecausedbyathyroidtumor,whichisusuallydetectedasalumpduringphysicalexamination.Thetreatmentforhyperthyroidismissurgeryincombinationwithadministrationofradioactiveiodine.相关激素间的协同作用1、协同作用：协同作用是指不同激素对同一生理效应都发挥作用，从而达到增强效应的结果。促进蛋白质合成和骨的生长甲状腺激素促进机体生长发育神经系统发育幼年不足侏儒症幼年不足呆小症生长激素甲状腺激素协同作用机体正常生长发育生长激素2.甲状旁腺维持钙稳定扁椭圆形黄豆大小，呈棕黄色，有上下两对，位于甲状腺侧叶后面的被囊上。Parathyroidglands:Manyyearsago,thefour,smallparathyroidglandsweresometimesmistakenlyremovedduringthyroidsurgery.Parathyroidhormone(PTH),thehormoneproducedbytheparathyroidglands,causesthecalcium(Ca)levelinthebloodtoincreaseandthephosphate(HPO)leveltodecrease.PTHpromotesbonebreakdownandcalciumretentionbythekidneys,andactivatesvitaminD,which,inturn,stimulatestheabsorptionofcalciumfromtheintestine.Italsopromotesthekidneys’excretionofphosphateinurine.Parathyroidhormoneinhibitstheactivityofosteoblastsandpromotestheactivityofosteoclastsinbone,therebyraisingthebloodcalciumlevel.Calcitoninhastheoppositeeffect,andtherefore,thehomeostaticbalanceofcalciuminthebloodisachievedthroughtheactionofbothhormonesIfinsufficientparathyroidhormoneisproduced,thebloodcalciumleveldrops,resultingintetany.Intetany,thebodyshakesfromcontinuousmusclecontraction.Theeffectisactuallybroughtaboutbyincreasedexcitabilityofthenerves,whichfirespontaneouslyandwithoutrest.Calciumplaysanimportantroleinbothnervousconductionandmusclecontraction.Itisalsonecessarytobloodclotting.

调节钙、磷代谢的激素有：

甲状旁腺素（parathyroidhormone,PTH）

由甲状旁腺分泌

降钙素（calcitonin,CT）

由甲状腺C细胞分泌

1，25-二羟维生素D3

由皮肤中7-脱氢胆固醇经日光中紫外线照射转化而来，也可由动物性食物中获取。

主要作用作用的靶部位分泌调节甲状旁腺素提高血钙降低血磷1.骨：促进骨细胞钙外流；促进破骨，动员骨钙入血。2.肾：促进肾小管对钙的重吸收，抑制磷的重吸收3.肠：加速小肠黏膜对钙的重吸收血钙和血磷浓度降钙素降低血钙和血磷1.骨：抑制破骨，减少溶骨，增强成骨。

2.肾：抑制肾小管对钙、磷的重吸收。3.肠：间接抑制小肠黏膜对钙的吸收血钙浓度1，25-二羟VD3提高血钙和血磷1.骨：对骨盐沉积和骨钙动员均有作用。

2.肾：促进肾小管对钙、磷的重吸收

3.小肠：促进小肠对钙的重吸收血钙和血磷水平Controlofcalcium(Ca)levels.Theopposingactionsofparathyroidhormoneandcalcitoninonbonebreakdownmaintainthehomeostaticlevelofcalciumintheblood.3.胰腺调节血糖水平

胰腺的胰岛组织的α细胞分泌高血糖素,β细胞分泌胰岛素。胰岛素：唯一降低血糖的激素。作用：促进糖元形成和抑制非糖物质转变为葡萄糖，降血糖。胰岛素的分泌受血糖的调节。高血糖素：作用：促进糖元分解和非糖物质转变为葡萄糖，升血糖。

Pancreas:Thepancreasisalong,softorganthatliestransverselyintheabdomenbetweenthekidneysandneartheduodenumofthesmallintestine.Itiscomposedoftwotypesoftissues:oneproducesandsecretesthedigestivejuicesthatarecarriedbytheductstothesmallintestine,andtheother,calledthepancreaticislets(ofLangerhans),producesandsecretesthehormonesinsulinandglucagondirectlyintoblood.Insulinissecretedbybetacells,andglucagonissecretedbyalphacells.Insulinissecretedwhenthebloodglucoselevelishigh,whichusuallyoccursimmediatelyaftereating.Insulinhasthreedifferentactions:Itstimulatesallcells,andinparticularfat,liver,andmusclecells,toabsorbandmetabolizeglucose.Itstimulatestheliverandmusclestostoreglucoseasglycogen.Itpromotesthebuildupoffatsandproteins,andinhibitstheiruseasanenergysourcesothattheywillbeavailableduringleanertimes.Asaresultofitsactivities,insulinlowersthebloodglucoselevel.Glucagonissecretedfromthepancreasbetweenmeals,anditseffectsareoppositethoseofinsulin.Glucagonstimulatesthebreakdownofglycogenandraisesthebloodglucoselevel.拮抗作用：拮抗作用是指不同激素对某一生理效应发挥相反的作用。血糖低时分泌胰高血糖素血糖高时分泌胰岛素通过拮抗作用，实现对血糖的调节，保持血糖含量相对稳定。120mg/100mlRegulationofbloodglucoselevel.Whenthebloodglucoselevelishigh,thepancreassecretesinsulin.Insulinpromotesthestorageofglucoseasglycogenandthesynthesisofproteinsandfats(asopposedtotheiruseasenergysources).Therefore,insulinlowersthebloodglucoseleveltonormal.Whenthebloodglucoselevelislow,thepancreassecretesglucagon.Glucagonactsoppositetoinsulin;therefore,glucagonraisesthebloodglucoseleveltonormal.胰岛素的分泌异常：缺乏：糖尿病，Ⅰ型糖尿病—注射胰岛素，Ⅱ型糖尿病。“三多一少”:多食、多尿、多饮、体重少。过高：低血糖。胰岛素缺乏时的三多一少症状胰岛素↓蛋白分解↑脂肪分解↑酮体生成↑酮血症酮尿酸中毒昏迷脱水体重↓(尿氮)口渴多饮高渗性利尿多尿(尿糖)多食血糖↑饥饿感能量不足糖氧化↓葡萄糖利用↓＞肾糖阈Diabetesmellitus:Diabetesmellitus(sugardiabetes)isthemostcommonillnessduetohormonalimbalance.Symptomsinclude:sugarintheurine;frequent,copiousurination;abnormalthirst;polyphagia,whichisexcessiveeating;rapidweightloss;generalweakness;drowsinessandfatigue;itchingofthegenitalsandskin;visualdisturbancesandblurring;andskindisorders,suchasboils,carbuncles,andinfection.Manyofthesesymptomsdevelopbecausecellsarenotmetabolizingsugar.Theliverfailstostoreglucoseasglycogen,andallofthecellsfailstoutilizeglucoseasanenergysource.Thismeansthatthebloodglucoselevelisveryhighaftereating,causingglucosetobeexcretedintheurine.Becausemorewaterthanusualisexcreted,thediabeticisextremelythirsty.Sincecarbohydratesarenotbeingmetabolized,thebodyturnstothebreakdownofproteinsandfatforenergy.Unfortunately,thebreakdownofthesemoleculesleadstothebuildupofketones.Ketonesareacidicmolecules,andtheirbuildupinthebodycausesanincreaseinacidlevels(acidosis).Thereductioninbloodvolumeduetoproductionofcopiousurineandtheacidosisduotoketonescaneventuallyleadtocomaanddeath.Thesymptomsofhyperglycemia(highbloodsugar)developslowly,andinterventioncanreversesymptoms.Therearetwotypesofdiabetesmellitus.IntypeⅠdiabetesmellitus(insulin-dependentdiabetesmellitus［IDDM］),thepancreasdoesnotproduceinsulin,requiringthediabetictohavedailyinsulininjections.Theseinjectionscontrolthesymptombutcanstillcauseinconveniences.Eitheranoverdoseofinsulinortheabsenceofregulareatingcaninducesymptomsofhypoglycemia(lowbloodsugar)becausethebloodsugarlevelisbelownormal.Sincethebrainrequiresaconstantsupplyofsugar,unconsciousnessresults.Thecureforlowbloodsugarisquitesimple:animmediatesourceofsugar,suchassugarcubeorfruitjuice,cancounteracthypoglycemiaimmediately.Obviously,insulininjectionarenotthesameasafullyfunctioningpancreasthatrespondsondemandtoahighglucoselevel