Hi Patientone
Just to add also that the the "o" is part of the word's origin and its correct pronunciation. I don't know why a lot of these double letters have been removed in US - the same happens for "ae" together - the a is removed.
The word comes from Latin oestrus - pronounced eestrus. Oestrogen should also be pronouned the same way ie "eestrogen". In US they have removed the "o" and now pronounce it with a short "e" as in "get", but this means the clue to its etymology is lost.
Well you did ask!!!!
Hurdity x