Uterine response to prostaglandin E2 under oral contraceptives

The effect of prostaglandin E₂ (PGE₂) on the non-pregnant human uterus was evaluated in 35 patients. The compound was administered both by the i.v. and intra-uterine routes. Two groups of volunteers were studied; fifteen cases who were under oral contraceptives and twenty women with normal ovulatory cycles. The latter group served as the control group. The uterus under the influence of oral contraceptives showed a markedly reduced response to i.v. injections of PGE₂ at all phases of the menstrual cycles. However, the response at mid-cycle to local instillation of the compound was contradictory in the two groups, i.e. local intra-uterine instillation of PGE₂ induced uterine stimulation in pill users as compared to the usually observed uterine inhibition in ovulatory (control) cases around mid-cycle. In the proliferative and luteal phases (early and late in the cycle), the response to intra-uterine injections was qualitatively similar in the two groups but greatly reduced quantitatively in the pill user group. The implications of these findings in certain physiological processes and pathological conditions related to reproduction are discussed.