The levonorgestrel intrauterine system: a clinical perspective from the UK.

The main contraceptive effects of this valuable product [the levonorgestrel intrauterine system (LNG-IUS)] are by endometrial suppression and changes to the cervical mucus and uterotubal fluid that impair sperm migration. The blood levels of LNG are very low, so progestogenic symptoms are uncommon. Most women still ovulate and in the remainder sufficient estrogen for health is produced from the ovary, even if they become amenorrhoeic, as many do; this is primarily a local end-organ effect and should be seen as a benefit. Although usable by selected nulliparae, it is ideal for the parous woman. It has unsurpassed efficacy, and return of fertility is rapid. Combining the best features of hormonal and intrauterine contraception, its gynecological benefits are impressive: the LNG-IUS user can expect a dramatic reduction in the amount and, after the first few occasionally troublesome months, in the duration of blood loss. Hemoglobin levels rise and dysmenorrhea is usually greatly benefited, unlike with current uterine ablation techniques. In perimenopausal women, it can protect the endometrium from overstimulation when estrogen replacement therapy (ERT) is added, by any chosen route. It thus provides a contraceptive modality of ERT with, usually, no bleeding and few progestogenic side effects-and is applicable before final ovarian failure. In summary, adverse side effects are few and in general they are not in the "hazardous" category. Regarding the admitted inconvenience of the first weeks of light postinsertion bleeding and the early phase low incidence of steroidal side effects: good counseling is paramount, since forewarned is forearmed!