Enzymeimmunoassayforthein-vitro-diagnosticquantitativedeterminationofProgesteroneinhumanserumandplasma.

Progesterone(pregn-4-ene-3,20-dione)isaC21steroidhormonecontainingaketo-group(atC-3)andadoublebondbetweenC-4andC-5.
Thissteroidhormoneisafemalesexhormonewhich,inconjunctionwithestrogens,regulatestheaccessoryorgansduringthemenstrualcycleanditisparticularlyimportantinpreparingtheendometriumfortheimplantationoftheblastocyteandinmaintainingpregnancy.
Innon-pregnantwomenprogesteroneismainlysecretedbythecorpusluteumwhereasinpregnancytheplacentabecomesthemajorsource.
Minorsourcesaretheadrenalcortexforbothsexesandthetestesformales.
ProgesteronecirculatesinbloodmainlyboundtoCorticosteroidBindingGlobulin(CBG),SexHormoneBindingGlobulin(SHBG)andAlbumin.Only2-10%ofthetotalconcentrationcirculatesasfreehormone.Bloodprogesteroneconcentrationsvarywidelyaccordingtothephasesofmenstrualcycle;theyarelowerthan1ng/mL(3.2nmol/L)inthefollicularphaseandaround10-20ng/mL(32-64nmol/L)inthelutealphase.
Themaximallevelsareachieved4-7daysafterovulationandremainelevatedfor4-6additionaldayspriortofallingtothepreovulatorylevels24hoursbeforetheonsetofmenstruation.
Sincetheriseandfallofprogesteroneparalleltheactivityofovarianfollicleandcorpusluteum,measurementsofplasmaprogesteroneareclinicallyusedtoconfirmovulationandnormalfunctionofthecorpusluteuminnon-pregnantwomen.
Ifovulationdoesnotoccurthecorpusluteumisnotformedandnocyclicalriseofprogesteroneinplasmaisobserved.Abnormalprogesteronesecretionhasbeenimplicatedinpremenstrualtension,irregularsheddingofendometrium,dysmenorrhoea,andlutealinsufficiency.
Progesteroneconcentrationcanvarynotonlyfromsubjecttosubjectbutalsointhesamepersonfromdaytodayorevenfromhourtohour.Consequently,ingynecologicaldisordersorabnormalpregnanciesserialmeasurementsratherthansingleonesarerecommendedforaproperinterpretationofresults.
Duringpregnancyprogesteroneiswidelyproducedbyplacenta,andplasmalevelsrisesteADIlyachievingvaluesashighas200ng/mLatterm.