Plasma Renin Activity and Aldosterone Secretion in a Pregnant Woman with Primary Aldosteronism

Abstract

Studies of plasma renin activity and aldosterone secretion were performed in a case of primary aldosteronism occurring during pregnancy. The patient had hypertension and severe hypokalemia. The aldosterone secretion rate was clearly elevated, even when compared with the levels seen during normal pregnancy. Plasma renin activity, rather than being elevated as in normal pregnancy, was suppressed to subnormal levels, whether compared with those of normal pregnancy or those of normal nonpregnant subjects. A definite preoperative diagnosis of primary aldosteronism was thus possible, using the usual criteria. The left adrenal gland, containing a benign cortical adenoma, was removed. Postoperatively, the patient's blood pressure and serum potassium concentration became normal. For 2 months, plasma renin activity and aldosterone secretion rates remained lower than the values observed in normal pregnancy. The fact that primary aldosteronism was associated with suppressed plasma renin activity during pregnancy indicates that this diagnostic criterion may be as valuable during pregnancy as in the nonpregnant state. It also indicates that the gravid uterus either contributes rather little to plasma renin activity of the pregnant woman or that the production of renin by the uterus, like that of the kidney, can be suppressed as a consequence of the hemodynamic changes of primary aldosteronism.