Yes, Mirena contains levonorgestrel, which is a progestin (synthetic progestogen).
Mirena is a levonorgestrel-releasing intrauterine system (LNG-IUS) that delivers the progestin levonorgestrel directly into the uterine cavity. 1
What is Levonorgestrel?
Levonorgestrel is a synthetic progestin (also called progestogen) chemically derived from 19-nortestosterone. It is approximately six times more potent than natural progesterone and has variable binding affinity to different steroid receptors 2.
How Mirena Works
The Mirena IUD releases 52 mg of levonorgestrel over its approved duration of use (5-8 years depending on indication) 3, 4. The device:
- Releases approximately 20 μg of levonorgestrel per day initially, declining to about 10 μg/day over time 5
- Creates local endometrial concentrations that are 200-800 times higher than those achieved with oral levonorgestrel contraceptives 2
- Results in lower systemic plasma levels compared to other levonorgestrel-containing contraceptive methods 2
Mechanism of Action
The contraceptive effect is achieved primarily through local progestogenic effects on the endometrium rather than systemic hormonal suppression 2:
- Endometrial thinning and glandular atrophy
- Stromal decidualization
- Thickening of cervical mucus
- Ovulation is maintained in most women (unlike combined hormonal contraceptives) 6
Clinical Classification
Multiple guidelines consistently classify Mirena as a progestin-based contraceptive method delivered via intrauterine route 1, 7, 4. It is distinct from combined hormonal contraceptives because it contains no estrogen—only the progestin levonorgestrel.
The term "progestin" and "progestogen" are used interchangeably in medical literature to describe synthetic compounds with progesterone-like activity, distinguishing them from natural progesterone.