The Greek, therefore the original, pronunciation has three syllables - this used to be the standard one in the UK and perhaps still is, but with US cultural imperialism rampant, I hae ma doots. In
America people seem to have assumed that the final -e is silent, as in
Katherine. In South
Africa I've never encountered the three-syllable version, to my regret; I prefer the sound of it. A while ago we had a woman on TV and radio who did sort of hostessing on game shows I think (rather vague about such things!) and she used the EYEreen version. All the other SA ones I've known have been eyeREENs.