The menstrual cycle in women using an intrauterine device.

The duration and hormonal characteristics of the menstrual cycles of women using Copper T intrauterine devices (IUDs) were studied. Daily load samples were obtained during both the pre- and postovulatory phases of 30 IUD-associated cycles and the hormone values were compared with those of 15 normally menstruating women not using contraception. The ovulation rate and peak levels of 17 beta-estradiol and luteinizing hormone (LH) were not significantly different between the two groups. The average number of days from the 1st day of menstrual bleeding to the LH peak (the proliferative phase) was longer in the IUD users. The number of days from the LH peak to the onset of menstrual bleeding (the luteal phase) was shorter in the IUD users. Because of the compensating nature of these statistically significant differences, the total cycle length appeared to be unchanged. At the time of menstruation, the plasma levels of both progesterone and 17 beta-estradiol were significantly higher among IUD users. It is concluded that the presence of an IUD does not influence ovarian function, but that ovarian steroid production and endometrial events become asynchronous.