Mechanism of action of the intrauterine contraceptive device: evidence for a specific biochemical deficiency in the endometrium

The precise mechanism of action of the intrauterine contraceptive device (IUCD) is uncertain. In this study we compared the circulating concentrations of a specific endometrial protein, placental protein 14 (PP14), in 62 women with an IUCD and 16 controls. The concentrations of PP14 were substantially lower in IUCD users. There was no difference in the concentrations of another and less specific endometrial protein, insulin-like growth factor binding protein-1 (IGFBP-1). There was no difference in PP14 concentrations between those women with and without intermenstrual bleeding. We conclude that the reduced concentrations of PP14 in IUCD users reflect defective endometrial function in these women, probably related to the contraceptive effect We propose that the measurement of PP14 might be a means of comparing the efficiency of different devices.