Hi Niamh
The uterine thickness limit is usually set for post-menopausal women as I understand - and I think 4.5 mm is the limit above which there can be concern. This would be for women on no HRT for whom endometrial thickening could be a particular problem. Also post-menopausal women on continuous combined HRT should aim to keep the lining below a critcial limit (although the tolerance maybe higher?). Abnormal bleeding is more of a concern than exact uterine thickness.
For women in your position (as well as those on cyclical HRT) - as you say, the lining will vary from very thin just after your bleed to quite a bit thicker just before progesterone withdrawal so provided it is all shed then nothing to worry about. The thing is - at least you are being monitored on this regime, (and by one of the top gynaes!) and that is what is most important. Even if your lining became a bit too thick (following your bleed) - you would be able to reduce it by a course of progestogen. Even if you had to take an increased dose occasionally for this purpose, at least you wouldn't be taking it all the time.
Duavive is good for prog intolerant women because it has no prog - but the only problem can be that the oestrogen is the equine horse oestrogens ( same as Premarin) and only comes in a fairly low dose (0.45 mg) - and you can't increase the dose without the other component ( which protects the uterus). However if you are with Nick Panay then he may also permit a more flexible regime under supervsion - but as this product is very new there are no long term data.
There have been other women on here using Zoladex so if you are interested then maybe start a new thread on this? I think donnacrichton is one so perhaps look at her posts?
I'm pleased that things seem OK for you at the moment anyway
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Hurdity x