Effects of oral contraceptive therapy on the renin-angiotensin system.

Abstract

During treatment with estrogenprogestogen oral contraceptive preparations, blood levels of angiotensin II measured by radioimmunoassay were elevated to three times the normal value. This marked rise in blood angiotensin II occurred within five days of commencing treatment, persisted during oral contraceptive therapy for three months, and fell to normal levels after cessation of treatment. Plasma renin activity and renin substrate showed similar elevations during treatment, and were significantly correlated with the levels of blood angiotensin II. Plasma renin concentration fell significantly during treatment, to about 50% of the control value, and was inversely correlated with the blood angiotensin II level. These observations demonstrate that the estrogen-induced rises in plasma renin substrate and renin activity during contraceptive therapy result in high circulating levels of angiotensin II, and provide confirmatory evidence for the concept that the concomitant suppression of renin secretion is related to rising blood angiotensin II levels. While the exact mechanism of contraceptive-induced hypertension remains obscure, the occurrence of such marked activation of the reninangiotensin system provides an appropriate background against which genetic and renal factors may accentuate or precipitate the development of hypertension in susceptible women.