Inordertoevaluatetheinvolvementofthethyroidglandinreproduction,thyroidfunc-tioningwasdescribedinfemalecultivatedJapaneseeel(Anguillajaponica)inprogressivestagesofsex-ualmaturationinducedbychumsalmonpituitaryhomogenate(SPH)treatment.Serumthyroidhor-mones,thyroxine(T4)andtriiodothyronine(T3)werealsomeasuredineachstage.Thyroidglandac-tivity(epithelialcellheight)washighbeforeSPHinjection(previtellogenicstage),furtherincreasingattheearlyvitellogenicstage,thereafterdecreasingtolatevitellogenicandmigratorynucleusstages.TheprofilesofbothT3andT4changedduringvitellogenesis,beinghighduringprevitellogenicandearlyvitellogenicstages,andsubsequentlydeclining,thusmimickingthyroidglandactivity.Theseresultssuggestthatthethyroidhasrelationwitheelovariandevelopmentduringartificialmaturation.
