I've been puzzling recently about the general priniciple usually touted in favour of the Mirena, that systemic absorption is minimal. This seemed at odds with the reports that some women (intolerant to synthetic progestogens) react badly to it (while others love it!). How could this be if there is almost no systemic absorption? How could such a device have such a powerful local effect – that it can stop periods way before menopause and yet be barely absorbed into the body? Also because I know from papers that I've read, that more actual progesterone (ie Utrogestan) is absorbed systemically (as shown by higher blood serum levels) when used vaginally than orally at the same dose - I decided to have a look at how much progestogen was actually absorbed from the Mirena.
When looking at the information on the company's website I was reminded that this product was of course developed primarily as a contraceptive and not for HRT initially. Therefore compared for example to the oral combined contraceptive pill – eg Microgynon 30 (150 mcg levonorgestrel) - absorption (from Mirena) is of course minimal! With the latter (the Pill) the maximum serum concentration is approx 10 times that of Mirena (after 1 year of Mirena – can't find info about max from the start). The CCP is approx 3-4 times more concentrated (in terms of systemic levels) than the levo mini pill eg Norgeston.
However I was surprised to find – but perhaps not so since I was pondering the above seeming anomaly - that actually compared to Femseven much more is absorbed systemically from the Mirena than the HRT patch. After 4 years the Mirena (on average) is still giving higher levels than Femseven.
There is also a complicated relationship with SHBG (Sex Hormone Binding Globulin) which I don't yet understand sufficiently so have only vaguely got the gist of it - but SHBG is affected by levo and levo binds to it and somehow alters the systemic levels of levo – but it also depends on how much levo is ingested.... aaagh!
However – the major advantage of the Mirena is that it provides contraception as well as endometrial protection, sorts out the heavy bleeding of peri-menopause, and in addition you can add in whatever oestrogen dose you like – so it is very flexible which Femseven sequi is not – it only comes as one 50 mcg dose and those damn Femseven patches don't seem to stick that well for some women as they need to be on for a week (I've never used this type!).
Absorption goes CCP>Mini Pill>Mirena>Femseven sequi/conti. I can upload the actual figures but they're not strictly comparable although when there is an order of magnitude difference it is obvious!
So – compared to the CCP levels of levo (from the Mirena) are much much lower, but if you are post-meno and only want or are happy on a medium dose HRT, are a bit sensitive to some synthetic progestogens, and have no problems with fibroids then maybe you'd be better off with Femseven..... and of course most women probably are completely unaffected by any of it and oblivious to the detailed scrutiny given to this topic by some of us
![Smiley :)](https://www.menopausematters.co.uk/forum/Smileys/extended/smiley.gif)
I got all the info from the Mirena website, and the Mirena and Femseven sequi/conti SPCs' ( “Summary of Product Charatceristicsâ€) – my go to info (section 5.2) for the pharmacokinetics of the hormone ( this being what happens to the hormone over time after it is taken into the body and how long it takes to break down), as well as the SPCs for Microgynon and Norgeston. I am hoping my understanding and interpretation is correct....
By the way this is not meant to put anyone off – but to clarify the whole issue around systemic absorption and not getting it from Mirena!!!
Hurdity x