Intrauterine Hormone-Releasing Systems

Abstract

The development of intrauterine contraceptive devices and oral contraceptives has been the major breakthrough in the history of modern contraception. The principle of combining the favourable effects of these two contraceptive methods has been approached by the introduction of intrauterine systems (IUSs) that release steroids. Several steroids have been tested in vitro and in animal models, including clormadinone acetate, medroxyprogesterone acetate, megestrol acetate, norethindrone, levonorgestrel and progesterone [4]. Only the latter two hormones have been utilised in progestogen-releasing IUSs that have reached extensive clinical trials and later been put into use. The first clinical trial of progesterone-releasing IUSs was published in 1970 [28]. Nilsson and co-workers [16] published the first clinical study with levonorgestrel-releasing IUS. These two intrauterine hormone-releasing systems demonstrated that it was possible to combine the favourable effects of oral contraceptives, i.e. good efficacy, decreased menstrual bleeding, decreased menstrual pain and less pelvic inflammatory disease, together with those of intrauterine devices, i.e. good compliance, long-acting method, reversible and no oestrogens.