Our home is 14y/o now, with 3 full baths. THANK G*D I had them spray a S/G-sheen paint during the build! It's still only a mid-grade builders-paint, but the SHEEN is the saving-grace here!!
(I've since repainted "My" bath with FPE!!)

>>> We've had NO problems with the paint/drywall BECAUSE OF the higher-sheen paint.
>>> Before doing anything though...wash your walls with POWDERED Dirtex...usually no need to rinse!
>>> Apply a top-notch primer...forget Kilz. Use Zinsser 123, or C2-One (if ya can find it!).
>>> Now, 2 full coats of a Satin or higher sheen, in a good paint-series.
>>> Let your new paint dry a day b4 a load of steam hits it. FULL cure can take a month.
>>> USE THE BATH FAN DURING SHOWERS!!

Faron

Make sure the coats do not go on too thick. As Faron says, even a very thin coat of latex will take days to cure thoroughly. It is also wise to de-gloss between coats of a high sheen paint to ensure the best adhesion of the second coat, which I do with a sanding block loaded with a really fine sand paper. If I'm doing a really big area, I will get some tinted primer for the first coat after the Bin because there is no need to sand that.

DO NOT use any "Liquid Deglosser" between coats!!!
* The VOC's and odor of this stuff will make ya loopy.
* Besides, it only temporarily "tacks-up" a surface. If you can't finish painting within ~15min. after applying this stuff...you're back to square 1. You've also polluted your environment for no purpose at all.
* Even if you used HIGH-gloss paint everywhere....your coats of paint shouldn't go on more than 2-4 hours apart.
* Applied in this time-frame, glossier paints tack to themselves just fine, b4 noticeable surface-drying gets "too dry".
* Even if you had to wait a day between coats, you're MILES ahead lightly scuff-sanding the wall!!. The actual physical profile from sanding is waaaayy better than uselessly introducing the horrendous voc-levels of deglossers, which, again, are only of temporary benefit...if that...

Faron