Hi Meeka, the other thread you posted the link for is helpful. Like Kathleen, some years ago & several years postmenopause, I was told by a Cons Radiologist (private hospital) that 4mm was the magic number above which further investigation (hysteroscopy & biopsy) was required. I had gone nearly a year on low dose sequential HRT without any bleeding but had suddenly started to get spotting & though bleeds were of course to be expected on a sequential regimen, we were not sure why the sudden change from no bleeds to spotting, hence the scan. My lining was only 1-2mm at that point, so no further investigation.
A year later on higher dose oestrogen, I had a little spotting after sex & was fast-tracked for another abdo/TVS, this time at an NHS hospital. Lining was 6mm straight after a scheduled bleed, so I was somewhat shocked & expected a hysteroscopy & biopsy, but the sonographer said she thought that measurement was acceptable on HRT, especially as the endometrium was regular with no abnormalities of concern, bar a small fibroid I'd had for many years. My GP & Gynae both deemed the outcome fine to my surprise & I wasn't required to have a hysteroscopy on that occasion. Like yours, my bleeds then got heavier over time on a long cycle regimen for progesterone intolerance. I suspected the lining was becoming thicker & for that reason reduced my oestrogen dose & cycle length while waiting for hysterectomy, the histology from which, albeit benign, proved my suspicion was right. I would speak to your GP, gynae or menopause specialist for expert advice on your particular situation.
Wx