What is the hormonal coil?

The Mirena® intrauterine system (IUS) or hormonal coil is a highly effective form of long-term contraception that combines the advantages of two other methods: first, it has the same advantages as the progesterone-only pill (lighter, less painful periods and none of the side effects that can be caused by the hormone oestrogen, such as weight-gain and breast tenderness). Secondly, it also shares the advantages of conventional (copper) coils (reliable contraception, directly in the womb, that lasts several years).

The hormonal coil is a small, T-shaped device made of bendy plastic. The arms of the ‘T’ are flexible, allowing it to be inserted easily into the womb by a doctor – and ensuring that it stays in place once it’s been fitted.

On the stem of the ‘T’ there is a plastic casing (green in the photos), which contains the active ingredient in the hormonal coil, a synthetic version of a hormone secreted by the corpus luteum (i.e. progesterone), called levonorgestrel. Levonorgestrel has been used in lots of contraceptive pills for some time, and is very well tolerated. Once the Mirena® has been fitted, it releases small amounts of levonorgestrel slowly and steadily over several years, where it goes directly to the lining of the womb.

At the bottom of the Mirena® there’s a little loop, on which two threads are fastened. You will be able to feel for these threads yourself. The threads also make it easier for a doctor to remove the coil.

Mirena® means that for five years you can have extremely reliable contraception without having to think about using contraception or taking a pill on a daily, weekly or monthly basis.

The hormone levonorgestel has other positive side-effects, see Advantages of the hormonal coil.