How does the hormonal coil work?
The Mirena® releases small amounts of the corpus luteum hormone Levonorgestrel right where it’s needed: in the womb.
The dosage is set to release 20 micrograms of levonorgestrel over 24 hours, which is 20-100 times less than in the contraceptive pill. In the pill, the hormones have to be at higher doses because they have to be metabolized and enter the blood stream before they can become effective.
The hormonal IUD works from day one, and works in three ways, making it very safe:
- The hormone levonorgestrel ensures that the cervical mucus stays thick (making a safe barrier) so that sperm can’t get into the womb to fertilise the egg. This also offers women a degree of protection against infection, as sperm sometimes carry bacteria.
- The lining of the womb stays thin and does not prepare for implantation of a fertilized egg. As there is no thickening of the womb lining, periods become significantly shorter and lighter or may stop altogether.
- The viability and mobility of any sperm that does manage to make it into the womb is impaired by the hormone levonorgestrel.
These effects stop as soon as the hormonal coil is removed and are no longer detectable. Women can conceive (again) in their first cycle after having the hormonal coil taken out.