From the Research
Mirena (levonorgestrel) intrauterine device has a minimal effect on Follicle-Stimulating Hormone (FSH) levels in most women, as evidenced by a study published in 2022 1, which found no significant differences in FSH levels between women who received Mirena immediately after an artificial abortion and those who received it 4-7 days after the onset of their first menstrual cycle after abortion. The localized action of Mirena, releasing a small amount of levonorgestrel in the uterus with limited systemic absorption, allows FSH levels to remain within normal ranges during use, enabling continued ovarian follicular development in many users. Some women may experience partial suppression of ovulation, particularly in the first year of use when hormone levels are highest. The primary contraceptive mechanisms of Mirena include thickening of cervical mucus, inhibition of sperm motility, and creating an unfavorable endometrial environment for implantation, rather than consistent suppression of FSH and ovulation. Key points to consider include:
- Mirena's effect on FSH levels is minimal, as shown in the 2022 study 1
- The device's localized action in the uterus limits systemic absorption and allows for normal FSH levels and ovarian follicular development
- Some women may experience partial suppression of ovulation, especially in the first year of use
- Mirena's contraceptive mechanisms do not rely on consistent suppression of FSH and ovulation, but rather on other factors such as thickening of cervical mucus and inhibition of sperm motility. It is essential to note that the most recent and highest quality study, published in 2022 1, provides the strongest evidence for the minimal effect of Mirena on FSH levels.