The BMS paper mentioned above on progestogens and endometrial protection doesn't specify what a 'high' dose of oestrogen is.
It does say that if a person is on a high dose of oestrogen then they should consider taking a higher dose of utrogestan (up to 200mg daily or 300mg over 12 days). I think it is deliberately vague because a) what is high for one person may not be for another due to absorption rates; b) it is acknowledging that some women do need a high dose of oestrogen; c) clinical judgement is needed as to what a patient needs based on how they react to the HRT regime (bleeding etc).
What I take from this paper and also the evidence from Newson Health is that there can be great variation in doses depending on the individual patient. Research shows that as little as 45mg a day of utrogestan, continually, can be enough to protect the uterus and prevent bleeding. Yet some women need up to 200 or 300mg utrogestan to achieve the same.
I think it demonstrates why flexibility along with close monitoring is really important. What we don't need is a 'one size fits all' approach doled out by doctors who are not prepared to monitor our progress, offer scans when needed etc.
This is why I am grateful that there are GPs, NHS and private, who are taking this area of medicine seriously and developing a stronger evidence base.
**45mg per day progesterone taken vaginally - just to be clear. This is why some women use 100mg utrogestan alternate days vaginally. Yet others need much higher doses and it suits them.**