"In this article the abbreviation IUCD refers to this whole group of contraceptives, and the terms Mirena and IUS will be used interchangeably.
Most IUCD's make a woman's periods heavier, but the Mirena makes periods lighter than usual. Because of this, it is frequently used as a treatment for heavy periods, even in women who don't need contraception. As can be seen in the picture, it is made of a light, plastic, T-shaped frame with the stem of the 'T' a bit thicker than the rest. This stem contains a tiny storage system of a hormone called Levonorgestrel. This hormone is also used in contraceptive pills such as Eugynon, Logynon, Microgynon, Ovran 30, Ovranette and Trinordial. In the Mirena, however, a much lower dose is released than when you take the Pill (about 1/7th strength), and it goes directly to the lining of the womb, rather than through the blood stream where it may lead to the common progesterone-type side effects
at 11:04 AM on Nov. 17, 2009