Human chorionic gonadotropin in intrauterine device users

Measurements of human chorionic gonadotropin (HCG), luteinizing hormone (LH), and progesterone were carried out by means of radioimmunoassays in 21 women with regular menstruating cycles, using an intrauterine device (IUD). Serum HCG was undetectable in 10 women. In 11 women very small amounts of HCG were detected, all under 3 mIU/ml. HCG curves were inactive and flat; in one case the highest level of HCG coincided with the LH peak; in another case HCG was detected in spite of lack of ovulation. These facts suggest a cross-reactivity of LH and no real presence of HCG.