Plasma Renin Concentration, Activity, and Substrate in Hypertension Induced by Oral Contraceptives1

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Abstract
Eleven women were found to be hypertensive while taking oral contraceptive preparations (OCP) containing estrogen and gestagen. Three months after discontinuing medication, blood pressure was normal in 4 of the patients (group A), was intermittently elevated or labile in 2 cases (group B), and remained persistently above normal in 5 cases (group C). While taking OCP, all 11 patients had elevated plasma angiotensinogen (renin substrate). Plasma renin activity (PRA) was significantly increased by oral contraceptives in all 3 groups of patients. Plasma renin concentration (PRC) was profoundly suppressed in groups A and B while taking OCP. PRC was significantly reduced in hypertensive women of group C but not to the same extent as in groups A and B. After stopping OCP for 3 months, all patients had normal levels of renin substrate in plasma. PRA fell into the normal range in all groups after stopping OCP. PRC increased in all groups after stopping OCP but did not reach average normal levels in groups A and B. Renin concentration showed normal postural responses both on and off OCP. In normotensive women taking OCP, the increases in renin substrate and PRA were indistinguishable from those observed in the hypertensive women. The PRC of the normotensive group receiving OCP was significantly below the normal mean, but did not fall as profoundly as in hypertensive groups A and B. We conclude that: 1) hypertension can be induced by OCP even though PRC is normally suppressed by a feedback mechanism which involves increased substrate concentration and a high rate of angiotensin generation in plasma (PRA); 2) a profound suppression of PRC in a hypertensive woman taking OCP indicates that the hypertension is probably reversible after stopping OCP, while hypertension tends to persist in patients with lesser degrees of PRC suppression; and 3) since most women do not develop hypertension while taking OCP, despite changes in the renin-angiotensin system, qualitatively and quantitatively like those observed in the hypertensive women, the changes in this system should be regarded as dynamic responses rather than controlling factors in the hypertension, until the adaptive response to OCP is more fully elucidated.

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