Concentration of cytosolic progesterone receptor (PR) was measured by means of an exchange procedure in the endometria of 80 women. Investigations carried out in 35 normal menstruating females showed a gradual increase of PR during the preovulatory and immediate postovulatory phases, decreasing to the lowest level at the end of the cycle. Measurements in endometrial samples obtained from women on combined hormonal contraceptives demonstrated a significant decline of PR concentration in the periovulatory phase resulting in a flattening of the sinusoid PR concentration curve. The stronger down regulation effect of the preparation containing 1.5 mg of dienogest is due to the higher progestogenic efficacy of dienogest in the respective dosage. We consider the down regulation phenomenon a useful means among others to characterize the progestogenic potency of a steroid.
PIP: Concentration of cytosolic progesterone receptor (PR) was measured by means of an exchange procedure in the endometria of 80 women. Investigation carried out on 35 normally menstruating females showed a gradual decrease of PR during the preovulatory and immediate postovulatory phases, decreasing to the lowest level at the end of the cycle. Measurements of endometrial samples obtained from women on combined hormonal contraceptives demonstrated a significant decline in PR concentration during the periovulatory phase which resulted in a flattening of the sinusoid PR concentration curve. The stronger "down regulation" effect of the preparation containing 1.5 mg of dienogest is due to the higher progestogenic efficacy of dienogest in its respective dosages. The authors consider this "down-regulation" phenomenon a useful means of characterizing the progestogenic potency of a steroid. (author's modified)