http://ajpendo.physiology.org/cgi/co...ull/274/1/E139
I'd read that before considering RU-486. The level of understanding that must be achieved before using stuff like this is quite high. The one graph alone shows the increase in plasma cortisol levels, which is a pretty common side effect of RU-486.
Using something like this for an extended period of time, say the duration of a cycle and perhaps in PCT can cause a variety of problems. Namely, cortisol suppresses immune function, and pharmacologically cortisol is used in this manner during organ transplants. Cortisol also inhibits the actions of insulin, and is strongly catabolic.
It would take further research to determine the dosing and increase in RU-486 but some serious attention would have to be paid in wei***ng the risks with the benefits of blocking progesterone receptors. Is it really worth the risk?