Hi 2cats
The only one that is bio-identcial to our own progesterone is - wait for it - progesterone! This is available as Cyclogest - which you've tried, and utrogestan which you've also tried. It is also available as a vaginal gel (Crinone) but doesn't seem to be licensed for use in UK as part of HRT - and there has hardly ever been anyone on it.
The main problem with progesterone ie utrogestan is taking it orally, as it has more side effects this way due to the metabolites produced from metabolism through the liver, Taking it vaginally as you plan to do - and which Mary G does and I do - minimises many of these side effects - although quite a lot of it gets into the system as less is lost through digestion.
Because it is very unstable (progesterone) it has to be given in large enough doses to do its job of keeping the lining thin - as it can't really replicate what the ovary does by pumping it out continuously during the menstrual cycle or pregnancy. There is one progestogen which is very close to our own but is more stable but is only available as part of combi HRT - this is dydrogesterone in Femoston. Some women who live abroad get it as Duphaston but is no longer available in this country (maybe online?). This is often better tolerated orally than utrogestan because it is taken in lower doses but being more stable it stays around in the system a bit longer than utrogestan which is eliminated very quickly.
If you are taking cyclical HRT then you will expect to get irritability during the changeover back to oestrogen only - as normal pms, but you don't want to have to suffer severe symptoms while taking the progestogen itself.
The licensed dose as you probably know is 200 mg x 12 days per cycle but if used vaginally it should be possilbe to take less than this - from limited research which shows it can be effective at lower doses. I would not take it for less than 10 days though and any variation from the licensed dose should be done under supervision of your doctor and a regular scan of the uterus. It also depends how much oestrogen you are using since the Utrogestan is given as one size fits all - but in reality the amount needed is dependent on how much oestrogen you are taking (as well as where you are in menopause, whether you have fibroids etc).
I used Cyclogest for several years but as time went on I got bad migraines with it - sometimes while taking it and almost always at the withdrawal stage. Utrogestan suits me much better - and I have only ever had this vaginally.
Some women swear by Levonorgestrel (in the Mirena and Femseven) and others by Provera - so it really is a question of suck it and see!!!
Hope this helps
Hurdity x