Endometrial estrogen and progestin receptors in women bearing a progesterone-releasing intrauterine device.

Endometrial biopsies were obtained from eleven volunteers bearing a progesterone-releasing intrauterine device (IUD). The mean treatment time was 4.1 yrs (range 1--5 yrs). Tissue samples were collected during the follicular phase of the cycle and assayed for estrogen and progestin receptors with [3H] estradiol and [3H] ORG 2058 (16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione) as the respective radioactive ligands. Both receptor values were significantly lower (p < 0.01) than those present in endometrial tissue of normally menstruating women. The steroid receptor concentrations measured (estrogen receptor 19.6 +/- 9.9 and progestin receptor 134.4 +/- 121/4 fmol/mg cytosol protein) from women with an IUD represented only about 20% of those in endometria of normal women. This result suggests that progesterone released from the IUD has a depressive action on the sex steroid receptor levels which may contribute to the contraceptive effectiveness of the IUD.