Hi jacig1957
If you want to look at the release rates of the progestogen in the Mirena over time then do have a look at the product info here:
https://www.medicines.org.uk/emc/medicine/1829/spc/mirena/Section 5.2 gives the pharmacodynamic properties - which means what happens to the active ingredient in the body over time. There is a table showing the estimated release rate which is given as 21 mcg per day at 24 and 60 days after insertion ( ie no decrease), 19 mcg per day after 1 year, 14 mcg per day after 3 years and 12 mcg per day after 4 years and 11 after 5 years. It needs to remain relatively high for it to protect the endometrium over the 4-5 years, though I can imagine it may be even higher for the first 3 weeks after insertion (these data are not given).
If you really want the detail it says this:
"
The pharmacokinetics of levonorgestrel itself have been extensively investigated and reported in the literature. In postmenopausal users of Mirena who were receiving non-oral concomitant oestrogen, plasma levonorgestrel concentrations have been 276 ± 119 pg/ml, 196 ± 87pg/ml and 177 ± 70 pg/ml at 56 weeks, 24 months and 48 months respectively. A half life of 20 hours is considered the best estimate although some studies have reported values as short as 9 hours and others as long as 80 hours. Another important finding, although one in agreement with experience with other synthetic steroids, has been marked differences in metabolic clearance rates among individuals, even when administration was by the intravenous route. Levonorgestrel is extensively bound to proteins (mainly sex hormone binding globulin (SHBG) and extensively metabolised to a large number of inactive metabolites."
Section 4.8 also gives the undesirable effects and their relative frequency. As this is going to be so much of an individual thing, what others tell you about their experiences will not tell you whether or not you will experience the same - but obviously very reassuring to hear good news stories! As already said, if after a few weeks it is clearly not suiting you and the side effects are far too severe, then you can always have it removed.
What I am puzzled about is why they are inserting it at the same time as removing the polyps and taking a biopsy without waiting for the results of the biopsy - but I guess that suggests possibly their confidence that it is likely the polyps that are causing your issues rather than anything sinister.
It also seems common practice to offer a Mirena to anyone who has to have hysteroscopy and biopsy for thickened lining - I was offered one twice, both times I had these procedures, and mine was without any anaesthetic, so that couldn't have been the reason (ie pop one in while she';s "out" !).
All the best
Hurdity x
