A risk-benefit assessment of the levonorgestrel-releasing intrauterine system.

The levonorgestrel-releasing intrauterine system (LNG-IUS), has been developed by Leiras Pharmaceuticals, Turku, Finland. It is a new systemic hormonal contraceptive that releases levonorgestrel 20 micrograms every 24 hours. The device provides fertility control comparable with that of female sterilisation, complete reversibility and convenience, and has an excellent tolerability record. The low dosage of levonorgestrel released by its unique delivery system ensures minimal hormone-related systemic adverse effects, which tend to be in the category of 'nuisance' rather than hazardous, and gradually diminish after the first few months of use. In some respects, the contraceptive characteristics of the LNG-IUS have over-shadowed a substantial range of noncontraceptive beneficial effects that are rarely seen with inert or copper-releasing intrauterine contraceptive devices (IUDs), and have important and positive gynaecological and public health implications. This applies particularly to the profound reduction in duration and quantity of menstrual bleeding, and alleviation of dysmenorrhoea, which are associated with the use of the device. Recent studies have shown that the LNG-IUS is effective in preventing endometrial proliferation associated with oral or transdermal estradiol therapy, and in inducing regression of endometrial hyperplasia. Further research is required to determine whether it has a role in regulating the growth of uterine fibroids, and preventing pelvic inflammatory disease. The unique unwanted noncontraceptive effects of the system, including possible development of functional ovarian cysts, and the relationship between menstrual bleeding pattern and ovarian function, also require better understanding, in order to offer appropriate patient counselling and maximise acceptability and continuation of use of the method.