| Kitsize | 96 |
| Method | RIA(CT) |
| Incubationtime | 1x1h |
| Standardrange | 1.7-1090µg/dL |
| Specimen/Volumes | 20µLSerum |
| Substrate/isotope | 125I<450kBq |
| RegulatoryStatus: | EU:CE |
Radioimmunoassayfortheinvitroquantitativemeasurementofhuman5-Androsten-3b-OL-17-DioneSulphate(DehydroepiandrosteroneSulphateorDHEASulphate)inserum.
Dehydroepiandrosterone(DHEA)anditssulphatedform,DHEA-S,arethemostabundantsteroidproductsoftheadrenalglands.Theadrenalisthesolesourceofthesesteroidsinwomen,butinmenthereisalsoasmallcontributionfromthetestes.FormationofDHEAisstimulatedbyACTHproducingasignificantdiurnalvariationinserumconcentrations.DHEAisrapidlyconvertedtoDHEA-Sbyanenzymepresentintheadrenals,liverandsmallintestine.DHEA-Sispresentatconcentrationsgreaterthan200timesthatofDHEAandhasalongerhalflife,whichlargelyremovesthediurnalvariation.
Theaginginfluencestheendocrinetemporalstructure,includingDHEA-SwhichcanbeconsideredasabioMarkerofaging,sinceitslevelsgraduallydecreaseinoldersubjects.PlasmalevelsofDHEA-Sincreasesteadilyfromabouttheseventhyearoflife,thangraduallydeclineafterthethirddecade.
DHEAisa19-carbonsteroidwithamolecularweightof288Kdandahalf-lifeinplasmaofabout1-3hours.ThemolecularweightofDHEA-Sis368.5Kdandthehalf-lifeisabout10-20hours.DHEAisformedfrompregnenolonebytheenzyme17,20desmolaseandmetabolisedtoandrostenedioneortestosteroneby3beta-or17beta-hydrosteroiddehydrogenaserepectively.HydrosteroidsulphataseconvertsDHEAtoDHEA-Sandsulphohydrolasereversesthisreaction.
ClinicalApplications
RaisedlevelsofDHEA-Sarefoundintheplasmaofpatientswithadrenaltumorsorwithcongenitaladrenalhyperplasia.DHEA-Smayalsobeslightlyelevatedinpatientswithpolycysticovaries,supportinganadrenalcomponenttothevirilizationseeninthiscondition.HCG-productiontumorsinmenmayleadtoincreasedtesticularDHEAproduction.
DHEA-Sisoftenassayedinconjunctionwithfreetestosteroneasaninitialscreenforhyperandrogenisminhirsutism.SometimesDHEA-Sistheonlyhormonecirculatingatalevelabovenormal,andisapparentlymorelikelytobeelevatedduringtheearlystagesofhirsutismthanmostotherandrogens.
DHEA-Sisusuallyundetectablewithadrenalinsufficiencyorpanhypopituitarism.ConcentrationsareslightlydecreasedinpregnancyandwithoralcontraceptiveuseandmarkedlydecreasedfollowingglucocorticoidadmiNISTration.
LowcirculatingconcentrationsareseenwithsevereillnessandinpatientswithAIDS.
