Well it's just the bottom half of this drawing again.
http://en.wikipedia.org/wiki/File:Steroidogenesis.svg
When you take maca, it increases DHEA. That is dehydroepiandrosterone in the drawing.
There are two ways to make testosterone from DHEA. Just follow the arrows in the drawing. Then aromatase makes the estrogens.
So what the bodybuilders are saying is true: when they take maca, the immediate effect is more testosterone. If they use an aromatase blocker, it will stay. If they don't, the testosterone will become estrogens in the end.
If you increase PM, your ovaries will make more estrogens. Wahaika explained here how that works:
http://beboard.proboards.com/index.cgi?board=Routines&action=display&thread=3029
(Scroll down to "Homeostasis")
If your ovaries make more estrogens, you will run out of DHEA after a while, because estrogens are made out of DHEA (I guess that's what the ovaries make it from too). Then you take maca to make more DHEA available. That will become testosterone, and then estrogen. If you're worried about the testosterone becoming
DHT and breaking you out, take an anti-androgen with maca.
The difference is males don't have ovaries. Wahaika's positive feedback loop will stimulate their testes to make more testosterone. They will also run out of DHEA, so the end result of taking more maca is the same as in females.