USMLE题库Endocrinology1-10

Endocrinology题库Q1A50-year-oldmalepresentstotheemergencyroomwithasuddensevereheadache,doublevision,andbitemporalhemianopsia.Hesaysthathe’shaddecreasedlibidoandmildheadachesforafewmonths.Asyouarepresentingtoyourattending，hedevelopscardiovascularcollapseanddies，despiteaggressiveresuscitation.Autopsywillmostlikelyrevealwhichofthefollowing?A.RuptureofberryaneurysmB.PituitaryhemorrhageC.PulmonaryembolismD.IschemicnecrosisofpituitaryE.AcutecongestiveglaucomaF.TemporalarteritisA1:Correctanswer:BThepatientdescribedinthevignettemostlikelyhadpituitaryapoplexy,whichisacutebleedingintoapreexistingpituitaryadenoma.Pituitaryapoplexyisamedicalemergency;withouttreatment,prognosisispoor.Symptomswillbebimodal;acuteandchronic.Thelong-standingsymptomsofapituitarytumorwillbepresentformonths,aswiththisman'sheadacheanddecreasedlibido;accompanyingthesechronicsymptomswillbeanacutepresentation,aswiththesevereheadacheandvisualdisturbancesinthispatient.Signsofmeningealirritationcanalsobeseeninpituitaryapoplexy,mimickingasubarachnoidhemorrhage.Acarefulphysicalexamcandifferentiateasubarachnoidhemorrhagefromasellarmasswithsuprasellarextension(pituitarytumor)bythepresenceofbitemporalhemianopsia,presentonlyinthelatter.PatientssufferingfrompituitaryapoplexydevelopcardiovascularcollapsebecauseACTHdeficiencyleadstoadrenocorticalinsufficiency.Anurgentneurosurgicalconsultationandtreatmentwithglucocorticoidsarerequired.(ChoiceA)Theruptureofberryaneurysmcanpresentsimilarlytopituitaryapoplexy,includingsignsofmeningealirritationandcranialnervepalsy.Asdiscussedpreviously,theseconditionscanbedifferentiatedbybitemporalhemianopsia,whichisspecifictopituitarylesions.AnMRIofthebrainwillbeverysensitiveindiagnosingeithercondition.(ChoiceC)Pulmonaryemboliusuallycauseshortnessofbreath,chestpain,andhypotension.Headacheanddiplopiaarenotthepresentingfeaturesofpulmonaryembolism.(ChoiceD)IschemicnecrosisofthepituitaryisalsoknownasSheehansyndrome,whichtypicallyaffectspostpartumwomen.Acuteheadachesandvisualfielddefectsdonotoccur;rather,mostpatientswithSheehansyndromepresentindolentlywithafailuretolactate.(ChoiceE)Acutecongestiveglaucomawillcauseeyepain,periorbitalheadaches,eyeredness,anddecreasedvision-butnotdiplopia.Circulatorycollapsedoesnotoccur.(ChoiceF)Thecharacteristicpresentationoftemporalarteritisisheadaches,jawclaudication,and-ifnottreated—visionlossduetoischemicopticneuropathy.Thepresentationisnotcatastrophicasseeninthepatientdescribedinthevignette.Q2A60-year-oldmancomestothephysicianwithdifficultyclimbingstairsanddyspneaonexertion.Healsocomplainsofgaining15kg(33lb)overthelastseveralmonths.Physicalexaminationrevealsdarkeningofhisskinandproximalmuscleweakness.Chestx-rayshowsalungmass.Laboratorystudiesrevealelevatedserumcortisolandadrenocorticotropichormonelevels.Whichofthefollowingadditionalstudieswouldbethemosthelpfulforestablishingthediagnosis?A.MagneticresonanceimagingofthebrainB.DexamethasonesuppressiontestC.Serumthyroid-stimulatinghormonelevelsD.AdrenocorticotropichormonestimulationtestE.Serumcortisollevelsat8:00AMA2Correctanswer:BTheworkupofendogenousCushingsyndromeinvolvesmeasuringadrenocorticotropichormone(ACTH)andcortisollevelsaswellasdexamethasonesuppressiontesting.CortisollevelsareelevatedinallpatientswithCushingsyndrome;ACTHlevelscanbehighorlowdependingontheetiology.PrimaryadrenaldiseasepresentswithsuppressedACTHlevelsduetointacthypothalamic-pituitaryfeedbackinhibition.However,CushingsyndromecausedbyapituitaryadenomaorectopicACTHsecretionwillpresentwithelevatedACTHlevels.High-dosedexamethasonesuppressiontestingcanhelpdistinguishbetweenthese2possibilities.PatientswithACTHhypersecretionfromapituitaryadenomaareonlyrelativelyresistanttoglucocorticoidfeedbackinhibition.Thus,high-dosedexamethasonesuppressiontestingwillcauseareductionincortisolandACTHlevelsinthesepatients.Incontrast,mostnonpituitarytumorsassociatedwithectopicACTHproductionarecompletelyresistanttofeedbackinhibition.BecausethispatienthaselevatedACTHlevels,dexamethasonesuppressiontestingwouldbethebestnextsteptofurtherdelineatethecauseofhisCushingsyndrome.(ChoiceA)ImagingstudiessuchasMRIorCTscanarenotusuallyperformedintheinitialevaluationofmostendocrinologicdisorders,includingCushingsyndrome.BiochemicalinvestigationcomesfirstintheworkupbeforeanyimagingasbrainMRIwillshowsmallmasslikelesions5%-10%ofthetimeeveninnormalsubjects(incidentalomas).(ChoiceC)Adiagnosisofhypothyroidismwouldnotexplainthispatient'selevatedcortisolandACTHlevels.(ChoiceD)TheACTHstimulationtestisusedintheevaluationofadrenocorticalinsufficiency,notadrenocorticalexcess.(ChoiceE)Innormalindividuals,serumcortisollevelsarehighestearlyinthemorninganddropsignificantlyintheeveninghours.However,inCushingsyndrome,thisnormalcircadianrhythmislost.Thus,measurementofcortisollevelsintheeveningismoresensitiveandspecificforCushingsyndromescreening,sincelevelsarenormallythelowestatthistime.Q3A32-year-oldCaucasianmalecomestoyourofficecomplainingofvisualproblems.Hehashadseveral•’near-misses”inhiscarlately,beingnearlyhitbycarscomingfyomboththe