Cushing’scontinuedfrompage27suppression.
Unfortunately,thismeasurementofbloodcortisolcanbe
affectedbythestressofspendingadayinthehospitalfor
repeatedbloodcollections.Forthisandotherreasons,
cortisolissometimesmeasuredinurine,whichcanbe
collectedathome.Complicatingthediagnosisisthefact
thatolderdogsmayhaveoneormorecoexistingdiseases
thataffecttheresultsofthescreeningtests.
“KikiwasdiagnosedwithbothCushing’sanddiabetes,which
havesimilarsymptoms.Adjustingthedosageofmedicationsfor
eachwascomplicatedanddidnotbringKiki’sdiseasesunder
control.Possibly,iftherehadbeenonlyonesignificantdisease
themedicationwouldhavebeenmoreeffective.Welearned
soonafterthosediagnosesthatshehadathirddisease,
hemangiosarcoma.Thistriplewhammywastoomuchtodeal
with.Sheratherquicklybecameblind,whichwasprobablyaside
effectofthediabetes.Shebecameaveryunhappy,uncomfortable
dogthatdraggedherselfaround.”
SeveralPBGVownersfounditchallengingtohave
theirdogsdiagnosedbecauselocalveterinarianshadlittle
experiencewiththedisease.Theyfounditnecessarytobe
referredtoatertiarycareveterinaryhospitalfordiagnosis
andtreatment.
HowisCushing’streated?Itisimportantto
determinewhetherthedoghasCushing’sduetoapituitary
oradrenaltumorbecausethetreatmentsandprognosis
differ.Magneticresonanceimagingorcomputerized
tomographyscanmayrevealthetumorandgiveadditional
informationonprognosis.Lessthan10percentofCushing’s
casesarecausedbybenignormalignanttumorsofthe
adrenal.Ifbenign,surgicalremovaloftheadrenalwillcure
thedisease.Theprognosisislessfavorableifamalignant
tumorhasspreadbeyondtheadrenal.
ThemostcommoncauseofCushing’sisatumorofthe
pituitarygland.Surgeryisnotusuallyanoptionforthis
tumor,butitmaybepossibletocontrolthisformofthe
diseasewithmedicationsthatregulatetheadrenalgland.
Vetoryl(Trilostane)wasapprovedbytheFDAin2008for
useindogswithCushing’s.Thisdrugblocksthesynthesis
ofcortisolintheadrenalwithoutharmingadrenalcells.It
appearstobesafeandeffective,withminimalsideeffects
thatcanincludevomiting,lackofenergy,diarrheaand
weightloss.
Anipryl(Selegiline)istheonlyotherFDA-approveddrug
forcanineCushing’s;itisalsoapprovedtotreatcanine
cognitivedysfunction.Aniprylblocksdopaminebreakdown
inthebrain.Theresultanthigherdopaminelevelsinhibit
ACTHsynthesisinthepituitary.Unfortunately,only
afractionofdogswithpituitarytumorsrespondto
Anipryltreatment.
PriortoapprovalofVetoryl,themostcommonlyused
drugwasahumanchemotherapydrug,Lysodren
(Mitotane),whichactsbydestroyingtheadrenalcellsthat
producecortisol.Lysodrenhasseveresideeffectsandwas
neverFDA-approvedspecificallyfordogs.
“WehadusedLysodrenwithmyfirstdogwithCushing’s.I
hadkeptuponmedicationsforthediseaseandwasawarethat
Trilostanehadbecomeavailable.ItoldmyvetthatIwantedto
treatPrincesswithtrilostane.Myvethadnotheardofitand
agreedtoitsuseonlyunderthesupervisionofalocalveterinary
internistwhowasusingitinhispractice.“
“MyfirstdogwithCushing’swastreatedwithLysodren.
Theseconddogstartedonitbutcameveryclosetodeveloping
Addison’sdisease(cortisollevelstoolow)andhasneverbeenon
medicineforCushing’sagain.Ihavehimtestedeverythreeto
fourmonthsand,touchwood,he’sbeenfine.Allofmydogs
getflaxseed,whichhasbeenrecommendedforatypical
canineCushing’s.”
Aspituitary-dependentCushing’sprogresses,the
pituitarytumormaygrowlargeenoughtocauseneurologic
symptoms,suchasdepression,circling,seizuresandother
behaviorchanges.
“InMarch,CharliehadwhatIthoughtwasaseizure.Hewas
unabletostandandhisbodytrembled,althoughhedidnotlose
consciousness.Thislastedaboutthreehours,afterwhichhe
appearednormal.Hespentseveraldaysinthehospitalhaving
testsandanultrasound,whichIrequestedasIthoughthemight
havecancer.Hecamehomewithnodiagnosis.Inowknowthat
theseizurewasastrokecausedbyCushing’s.Thefollowing
month,CharlieappearedmildlydepressedsoItookhimbackto
thehospital.TheysuggestedIwaitandsee.Irequestedafull
thyroidpanelbedone,butitshowednothing.ByJune,Charlie
haddeterioratedquitequickly.Ididalotofsearchingonthe
computeranddecidedhehadmanysymptomsofCushing’s.
Armedwithmypaperwork,Ireturnedtothehospitaland
requestedaCushing’stest.Charlieendedupwithclassic
Cushing’ssymptoms:lossofcoat,potbelly,bonyheadand
alteredmusclemass.HestartedtakingtrilostaneinJune.”
“JoujoustartedonTrilostaneandwithinaweek,shebecame
deathlysickwithvomiting.Wethoughtweweregoingtoloseher.
ShewasgivenCereniaforthevomiting.Bloodworkwasdone
28
www.pbgv.org
Winter2014
ISaberTails
Glossary
ACTH–adrenocorticotropichormoneisaproteinsecretedby
thepituitaryinresponsetobiologicalstress.Itbindstocellsin
theadrenalglandandleadstoincreasedadrenalproduction
ofcorticosteroids,suchascortisol.
Cortisol–asteroidhormoneproducedbytheadrenalgland
thatcirculatesthroughoutthebody.Itsprimaryfunctionsare
toincreaseglucosesynthesis,suppresstheimmunesystem,
andincreasemetabolismoffat,protein,andcarbohydrate.
Endocrine–relatingtothecollectionofglandsthatsecrete
hormonesintothecirculatorysystem.
Hormone–amoleculeproducedandsecretedbyagland,
circulatesthroughoutthebody,andregulatestheactivityof
distantcellsororgans.
Hyperadrenocorticism–thesyndromeofhavingexcess
adrenalhormonescirculatinginthebody.Hyperadrenocorticism
isalsoknownasCushing’ssyndrome.
References
Behrend,Kooistra,Nelson,Reusch,andScott-Moncrieff
(2013)Diagnosisofspontaneouscaninehyperadrenocorticism:
2012ACVIMconsensusstatement(smallanimal).JVetIntern
Med27:1292-1304.
Bellumori,Famula,Bannasch,Belanger,andOberbauer
(2013)Prevalenceofinheriteddisordersamongmixed-breed
andpurebreddogs:27,254cases(1995-2010).JAVMA
242:1549-1555.
FoodandDrugAdministration.TreatingCushing’sdiseasein
dogs.www.fda.gov/forconsumers/consumerupdates/
ucm151209.htm
KooistraandGalac(2012)Recentadvancesinthediagnosis
ofCushing’ssyndromeindogs.TopicsinCompanAnMed
27:21-24.