I have always said it like 'io-deen' because whenever 'ine' is used (eg. amine, or fluorine) it is said that way. Sometimes I'm corrected by people who think it should be pronounced 'io-dyne', which is correct?
Manshu is correct,in British English we pronounce iodine as in seen while in North American English we pronounce it as in mine.
Or we could just use German. In German they do not use the suffix for halogens at all so that "iodine" is just "Jod". Now all we have to remember is that you don't pronounce the long "i", instead using the usual "j"/"y" consonant sound.
Like the other halogens, iodine is pronounced eye - o - deen (especially by chemists) .
Who are you talking to? To non-chemists (in the US), just say i-oh-dyne.
But if you are talking with chemists, say i-oh-deen.
If you are talking to a mix of chemists and non-chemists, decide which you would like to be classified as.
Or, you could say "element 53".
Think about how other halogens are pronounced: fluor-een, chlor-een, brom-een, astat-een, and newly named tenness-een. Why would it be io-dyne and not iod-een?