Glucose Tolerance Test.ppt

Glucose Tolerance Test

1. Glucose Tolerance Test
Amit Kumar Singh
Assistant Professor
Department of Medical Lab Technology
Chandigarh University, Punjab

2. Introduction
•OGTTmeasuresthebody'sabilitytouseglucose,thatisthebody's
mainsourceofenergy.
•AnOGTTcanbeusedtodiagnoseprediabetesanddiabetes.
•Usedtotestfordiabetes,insulinresistance,impairedbetacell
function,andsometimesreactivehypoglycemiaandacromegaly,or
rarerdisordersofcarbohydratemetabolism.
•AnOGTTismostcommonlydonetocheckfordiabetesthatoccurs
withpregnancy(gestationaldiabetes).
•ManyvariationsoftheGTThavebeendevisedovertheyearsfor
variouspurposes,withdifferentstandarddosesofglucose,different
routesofadministration,differentintervalsanddurationsof
sampling,andvarioussubstancesmeasured

3. Who needs a glucose tolerance test?
•Allwomenforgestationaldiabetes(betweenthe24thand28thweek
ofyourpregnancy)todetectcomplications
•Doctormayalsorecommendthatsomeonehavethistestiftheyare
havingthesymptomsofprediabetesordiabetes.
•Havehadgestationaldiabetesduringapreviouspregnancy.
•Havepreviouslygivenbirthtoababywhoweighedmorethan4.1kg
•Areyoungerthanage25andoverweightbeforegettingpregnant.
•Diagnoseprediabetesanddiabetes

4. Preparation
•Eatabalanceddietthatcontainsatleast150grams(g)of
carbohydrateperdayfor3daysbeforethetest.
•Fruits,breads,cereals,grains,rice,crackers,andstarchyvegetables
suchaspotatoes,beans,andcornaregoodsourcesofcarbohydrate.
•Donoteat,drink,smoke,orexercisestrenuouslyforatleast8hours
beforeyourfirstbloodsampleistaken.
•Telldoctoraboutallprescriptionandnonprescriptionmedicinesyou
aretaking.Drmaybeinstructtostoptakingcertainmedicinesbefore
thetest.
•Theglucosetolerancediagnostictestmaytakeupto3-4hours.
•Sinceactivitycaninterferewithtestresults,youwillbeaskedtosit
quietlyduringtheentiretest.
•Donoteatduringthetest.Youmaydrinkonlywaterduringthistime.

5. Introduction
•Mustremainseatedquietlyfor30minutesbeforeandduringthetest.
•Youarerequiredtoremaininthecollectioncentreuntiltheprocedure
iscompleted.
•Bringsomereadingmaterialorotheractivitytopassthetime.
•Iffeelunwellduringthetest,pleaseinformthecollectionstaffasyou
maywishtoliedown.
•Thereshouldnoacutesignificantillnessfor2weekspriortotest.
•Duetothenatureofthetest,testingisgenerallydoneinthemorning.
•Beforedrinkingtheglucose,pleaseinformthecollectionstaffifhave
anyallergies.

6. Procedure
•Azerotime(baseline)bloodsampleisdrawn.
•Thepatientisthengivenameasureddoseofglucosesolutiontodrink
withina5-minutetimeframe.
•Bloodisdrawn&urineiscollectedatintervalsformeasurementof
glucose(bloodsugar),andsometimesinsulinlevels.
•Theintervalsandnumberofsamplesvaryaccordingtothepurposeof
thetest.
•Forsimplediabetesscreening,themostimportantsampleisthe2hour
sampleandthe0and2hoursamplesmaybetheonlyonescollected.

7. •Ifyouaretakingthe50-gram,orone-hourtest,theywilltakeyourbloodsample
afteronehour.
•Ifyouaretakingthe75-gram,ortwo-hourtest,theywilltakeabloodsample
everyhourfortwohours.
•Ifyouaretakingthe100-gram,orthree-hourtest,theywilltakeabloodsample
everyhourforthreehours.

8. Results
Normal glucose levels
•50-gram(one-hourtest):equalorlessthan140mg/dL
•75-gram(two-hourtest):
•Fastinglevels 70-100mg/dL;
•One-hourlevels Lessthan200mg/dL;
•Two-hours Lessthan140mg/dL
•100-gramtest(three-hourtest):
•Fastinglevels Lessthan95mg/dL;
•One-hourlevels Lessthan180mg/dL;
•Twohours Lessthan155mg/dL;
•Threehours Lessthan140mg/dL

9. Normal GTT values
Normal glucose tolerance test values
75 g of glucose
Fasting:
Less than or equal to 100 milligrams per deciliter (mg/dL)
or 5.6 millimoles per liter (mmol/L)
1-hour:
Less than 184 mg/dL or less than 10.2 mmol/L
2-hour:
Less than 140 mg/dLor less than 7.7 mmol/L
Glucose tolerance diagnostic test (for gestational diabetes)
Values that indicate gestational diabetes.
75 g of glucose
Fasting:More than or equal to 92 mg/dL or 5.1 mmol/L
1-hour:More than or equal to 180 mg/dLor 10.0 mmol/L
2-hour:More than or equal to 153 mg/dL or 8.5 mmol/L
100 g of
glucose
3-hour:More than or equal to 140 mg/dLor 7.8 mmol/L

10. High glucose levels may be caused by
•Diabetes.
•Gestationaldiabetes.
•Hyperthyroidism.
•Somemedicines,suchascorticosteroids,niacin,phenytoin(Dilantin),
somediuretics,andsomemedicinesusedtotreathighbloodpressure,
HIV,orAIDS.
•Largeamountsofthehormonecortisolintheblood(Cushing's
syndrome).
•Inheriteddiseases,suchashemochromatosis.

11. Low glucose levels may be caused by
•Certainmedicines,suchasmedicinesusedtotreatdiabetes,
somebloodpressuremedicines(suchaspropranolol),andsome
medicinesfordepression(suchasisocarboxazid).
•Decreasedproductionofthehormonescortisolandaldosterone
(Addison'sdisease).
•Problemswiththethyroidglandoranunderactivepituitarygland.
•Atumororotherproblemsofthepancreas.
•Liverdisease.

12. What Affects the Test
•Smoking.
•Alcoholintake
•Recentsurgery,illnesses,andinfectiousdiseases.
•Weightlossthroughdieting.
•Longperiodsofbedrest(suchasfromahospitalizationorillness).

16. Insulin tolerance test
•Aninsulintolerancetest(ITT)isamedicaldiagnosticprocedureduring
whichinsulinisinjectedintoapatient'svein,afterwhichbloodglucose
ismeasuredatregularintervals.
•Thisprocedureisperformedtoassesspituitaryfunction,adrenal
function,andsometimesforotherpurposes.
•AnITTisusuallyorderedandinterpretedbyendocrinologists.
•Insulininjectionsareintendedtoinduceextremehypoglycemiabelow
2.2mmol/l(40mg/dl).
•Inresponse,ACTHandGHarereleasedasapartofthestress
mechanism.
•ACTHelevationcausestheadrenalcortextoreleasecortisol.
Normally,bothcortisolandGHserveascounterregulatoryhormones,
opposingtheactionofinsulin,i.e.actingagainstthehypoglycemia.

17. High glucose levels may be caused by
•ThusITTisconsideredtobethegoldstandardforassessingthe
integrityofthehypothalamic–pituitary–adrenalaxis.
•SometimesITTisperformedtoassessthepeakadrenalcapacity,e.g.
beforesurgery.
•DifferentiationofCushing'ssyndromefrompseudo-Cushing's
syndromesegdepression,alcoholexcess.
•Thistestispotentiallyverydangerousandmustbeundertakenwith
greatcare,becauseitcaninducethediabeticcoma.
•Ahealthprofessionalmustattenditatalltimes.
•Otherprovocationtestswhichcausemuchlessreleaseofgrowth
hormoneincludetheuseofglucagon,arginineandclonidine.

18. Side effects
•Sweating,palpitations,lossofconsciousnessandrarelyconvulsions
duetoseverehypoglycaemia.
•Oncehypoglycaemiahasoccurred,pituitarystimulationwillhave
occurredandivglucoseshouldbegivenifextremesymptomsare
present.
•AnAddisoniancrisismaybeprecipitatedinsubjectswithnoadrenal
reserve.

19. Preparation
•Thepatientshouldfastovernight(waterpermitted)andberecumbent
duringthetest.
•ECGmustbenormalandthepatient'sweightknown.
•Thesideeffectsofthetestshouldbeclearlyexplainedtothepatient.
•Insulindose
•0.15U/kgforsubjectswithnormalpituitaryfunction
•0.10U/kgforhypopituitarysubjects
•0.2-0.3U/kgforsubjectswithacromegaly,diabetesorCushing's
0.2-0.3U/kg for subjects with acromegaly, diabetes or Cushing's
0 minutes take 3 mL blood in plain tubes for GH, cortisol and 1 mL in fluoride tube
for glucose and inject insulin iv.
30,45,60,90,120
min
take 3 mL blood in plain tubes for GH, cortisol and 1 mL in fluoride tube
for glucose.

20. Interpretation
•Thetestcannotbeinterpretedunlesshypoglycaemia(<2.2mmol/L)is
achieved.
•Hypopituitarism:Anadequatecortisolresponseisdefinedasariseto
greaterthan550nmol/L.
•Patientswithimpairedcortisolresponsesie<550but>400nmol/L
mayonlyneedsteroidcoverformajorillnessesorstresses.
•AnadequateGHresponseoccurswithanabsoluteresponse>20mU/L
(7µg/L).
•Cushing'ssyndrome:Therewillbeariseoflessthan170nmol/Labove
thefluctuationsofbasallevelsofcortisol.