Effects of estrogens and progestogens on the renin-aldosterone system and blood pressure.

Endogenous 17 beta-estradiol (E2) and low parenteral doses of exogenous E2 are vasodilators. High dose estrogens, especially ethinylestradiol (EE) and mestranol, stimulate the synthesis of hepatic proteins including coagulation factors, sex hormone binding globulin, and angiotensinogen (Aogen). In the steady state, high plasma levels of Aogen produce only a very small increase of angiotensin II (AII) and plasma renin activity, because AII inhibits the secretion of renin and lowers plasma renin concentration. However, the increase in AII is sufficient for a slight reduction in renal blood flow and a slight increase in exchangeable sodium and blood pressure; in susceptible women, blood pressure may rise considerably. Effects of estrogens on the brain may also be involved in blood pressure changes. Endogenous progesterone is a mineralocorticoid receptor antagonist. Endogenous or exogenous progesterone leads to sodium loss and a compensatory increase in renin secretion, plasma renin activity, AII, and plasma aldosterone, e.g. in the second half of the menstrual cycle. Synthetic progestogens are commonly devoid of the mineralocorticoid receptor antagonistic effect of progesterone, and some are weak estrogen receptor agonists. Combined use of EE and synthetic progestogens may therefore enhance estrogen effects on body sodium and blood pressure. A new progestogen (Drospirenone) with an antimineralocorticoid effect like that of progesterone is described that slightly lowers body weight and blood pressure in a contraceptive formulation together with EE. An almost ideal oral contraceptive would be progestogen like Drospirenone together with a low dose natural estrogen that does not stimulate Aogen synthesis. Since most oral formulations for postmenopausal estrogen replacement also stimulate hepatic protein synthesis (including Aogen) to some extent, the transdermal route of E2 application for contraceptive purposes should also be investigated, since it has reduced potential for undesirable side effects.