OVARIAN-FUNCTION AFTER 7 YEARS USE OF A LEVONORGESTREL IUD

Fifteen women with regular menstrual periods and seven amenorrheic wom en who had been using a levonorgestrel-releasing (LNg) IUD for more th an seven years were studied. For controls, eight women using TCu380Ag IUDs for more than seven years were studied during two complete menstr ual cycles. Ovarian function was assessed with hormonal determination and ultrasound examinations. The regularly menstruating women were stu died for two complete menstrual cycles and the amenorrheic women for e ight weeks. In the regularly menstruating LNg-IUD users, according to progesterone levels, 93% of the cycles were ovulatory but just 58% of these 'ovulatory' cycles showed normal follicular growth and rupture. Follicular cysts and luteinization of regressing follicles were observ ed in 42% of the 26 'ovulatory' cycles studied. SHBG capacity was decr eased in the LNg-IUD users compared with the TCu380Ag users. Progester one levels were lower in the LNg-IUD users compared with the TCu380Ag users but this difference was not statistically significant. Preovulat ory estradiol and LH levels were lower in the LNg-IUD users than in th e TCu380Ag users. These differences were not statistically significant . For the amenorrheic women, five had follicular cysts that disappeare d spontaneously within 45 days. Two women showed follicular developmen t and rupture. The presence of good cervical mucus was observed in 69% of the ovulatory cycles studied in the LNg-IUD users. This indicates that effects on cervical mucus cannot be the main mechanism of action of the LNg-IUDs. It is concluded that LNg-IUDs may exert a contracepti ve effect in many different ways, such as inhibition of ovulation, end ometrial changes preventing implantation, alteration of physical and c hemical properties of cervical mucus affecting sperm transport and sub tle disturbances in hypothalamic pituitary ovarian function, resulting in alterations of follicular development and rupture.