We just started having this "problem" but the wife is not post menopause yet. It seems as the change started her desire did not change but we noticed a few odd things that needed checked out. She turned out to have thyroid issues (just diagnosed recently) and while being treated (and they just readjusted med dosages) lost a lot of her desire. She still wants it but not nearly as much as before she started treatment and would like to get back to the point she was at before. She did mention this to her Gyno at her yearly appointment and she suggested (and we were already of this mindset) we wait till the thyroid is where it needs to be and levels out then we can work on that problem. Kind of a one thing at a time deal. That of course leaves me to research things as I have the time for when we get to that point.
I said this so you know you are not alone in this and as mentioned by others there are treatments (the wife is currently not on any yet but wants to be). The best suggestion is to talk with a doctor and if needed find another until you get one who understands the problem and offers to work towards a solution.

