The levonorgestrel intrauterine system: the benefits of reduced bleeding

The levonorgestrel intrauterine system (LNG-IUS) offers a new therapeutic concept that combines a highly efficient contraceptive with a treatment that reduces menstrual blood loss in both normal women and those with menorrhagia. Initially developed to decrease the risk of expulsion of the intrauterine contraceptive device by reducing myometrial contractility, recent clinical studies have shown that the LNG-IUS provides excellent contraception without many of the adverse effects associated with the conventional intrauterine contraceptive device. The main mechanism of action of the LNG-IUS appears to be at the level of the endometrium, where the high dose of local progestogen causes decidualization, epithelial atrophy and direct vascular changes. Whilst some women experience systemic hormonal effects, circulating concentrations of levonorgestrel are low in comparison to those seen after the levonorgestrel progestogen-only pill. The LNG-IUS results in a dramatic reduction in menstrual blood loss. In turn, this has led researchers to investigate the LNG-IUS as an alternative to surgery for the treatment of dysfunctional uterine bleeding, uterine fibroids and adenomyosis. The system has also been used as a means of delivering progestogen for endometrial protection in postmenopausal hormone replacement regimens. The main side-effect of the LNG-IUS is irregular breakthrough bleeding. This is most common in the first 6 months after insertion. Detailed counselling is crucial to explain this anticipated effect, in order to reduce unnecessary discontinuation of treatment. After 6 months' treatment with the LNG-IUS, 20% of women become amenorrheic, rising to 50% after 5 years. Again, it is important to explain that this is an expected phenomenon, that it is not related to disorders of the hypothalamic-pituitary-ovarian axis, and that this 'bleed-free' status might indeed be viewed as a positive feature in its own right.