Hi mic 67
First if you start HRT before you reach natural menopause ( 12 months without a natural period) then you don't know if you are post-menopausal or not. Lack of bleeding on HRT does not necessarily mean you wouldn't have bled if you weren't on it though if you were still ovulating naturally you might have expected a bleed at some point as you are on a standard HRT regime.
You haven't said what your oestrogen dose was? Some women do not bleed even on sequential HRT - this happened to me in my later 50's having started HRT before menopause, having withdrawal bleeds for the first few years and then these petered out. However you were on a lower than licensed oral dose (it should be 200 mg oral Utro per day for 12 days per 28 day cycle) so that could also explain the lack of bleed? I would have thought you would have bleed earlier though if the lining was overthickening?
The amount of thickening of the womb lining is dependent on the oestrogen dose so on lower doses the lining may not have built up sufficiently to bleed. Under the normal or artificial (through HRT) cycle the womb lining will build up during the first two weeks of the cycle from the oestrogen. During the progesterone phase the lining changes structure ( ready for a fertilised egg). Then when the progestertone is stopped the lining breaks down and comes away as a bleed - a natural period or the HRT withdrawal bleed.
If the lining doesn't build up very much then theoretically the progesterone may act also to thin it down so when it is withdrawn you don't bleed ( as in my case).
Crucially though - because the thickness of the womb varies throughout the cycle - then the scan will reflect this =- depending on when it is taken. The best time to have a scan is immediately following the beed - or in your case if you didn;t have a bleed - straight after the end of the progesterone phase or a few days later ( if you would be waiting for a bleed). If you have a scan at the end of the oestrogen phase or early in the prog phase (and sometimes for the whole of it) then it will be at its thickest.
So as Nas says - the heavy bleed will not necessarily thin the lining completely and indeed the fact that it happened after only a week rather than on withdrawal of the prog after a complete 12 day course = indicates that the lining had thickened ( as per the scan) and needed to come away.
No its not a post-menopausal bleed as such but usually any unexplained bleeding after a period of time without bleeding - even when on HRT - would be referred. You say you are not convinced a referral is needed - but you went to the doc ( which triggered the referral) so you must have been concerned?
As you say it is most likely to be down to the change in delivery of the progesterone but also indicated that the 100 mg per day oral dose was not doing its job (eventually without change in regime your lining may have overthickened and then you would have bled perhaps randomly or heavily at the end of a later cycle - hard to say?).
I would always go for any consultation offered - because what it the harm in being monitored and checked that all is well - but equally I would be unduly worried because the explanation (change in prog) is reasonable.
However in order to know whether the lining has properly thinned down you would need to complete another cycle eg of vaginal prog and then have another scan immediately post-bleed.
Hope this helps and all the best
Hurdity x