Polyestriol phosphate (PE3P, SEP), sold under the brand names Gynäsan, Klimadurin, and Triodurin, is an estrogen medication which was previously used in menopausal hormone therapy (i.e., to treat menopausal symptoms in postmenopausal women) and is no longer available.

[1][2][3][4][5][6][7][8][9][10][11][12] PE3P has been used at a dosage of 40 to 80 mg by intramuscular injection once every 4 to 8 weeks in menopausal hormone therapy.

[5][14] The effects of PE3P on the vagina, uterus, pregnancy, prostate gland, coagulation, and fibrinolysis, as well as on mammary and endometrial cancer risk, have been studied.

[18][19][20][21][22][23][24][25][16] The endometrial proliferation dose of PE3P over 14 days in women is 40 to 60 mg by intramuscular injection.

[17] PE3P was developed by the Swedish pharmaceutical company Leo Läkemedel AB in the 1960s.