When we reach menopause and have no periods for 1 year -> things don't just stop.
The point at which our body can give enough prog to force a period has passed.
However that is not to say we completely stop producing hormones!
We still produce lower levels of both. Just not enough prog to produce a monthly bleed.
Therefore woman who continue into menopause are in effect in a situation where any further estrogen is potentially unopposed.
That is there is not enough prog in our system to stop its action and produce a healthy monthly bleed.
When estrogen only is given (not something done very often) then that increases the risk of this uterine cancer if no prog is given.
Therefore if we take away that unopposed risk by using either sequi or conti HRT then we further reduce the risk of long term unopposed exposure due to naturally remaining estrogen in our bodies.
If we look at the conti option the reason that its even better than sequi is that its continual giving prog and completely opposing the estrogen all the time.
This is why conti in most ladies using it thins the walls of our uterus.
So to summarise we are basically relying on luck without HRT after menopause and hoping that behind things we are not seeing a build up thats quietly growing away (potentially giving rise to a greater risk).
This is why a lot of ladies find themselves having severe periods once they commence HRT (after either a short gap or longer gap in periods).
I've seen some posts blaming it on the HRT, when in fact its just their bodies have been quietly building up awaiting enough prog to come along
Just a followup quote from Cancer Research UK's site:
"Oestrogen without progesterone to balance it increases the risk of womb cancer. Doctors call this unopposed oestrogen. The body stops making progesterone after the menopause, but still produces a small amount of oestrogen. So this explains why womb cancer is much more common in women after the menopause."