Essential hypertension with low conjugated catecholamines imitates pheochromocytoma.

SUMMARY The correlation between the degree of conjugation of plasma noreplnephrine (NE) and epinepbrine (E) and the clinical features of sympathetic hyperactivity was studied in 38 essential hypertensive patients from a referral population biased toward pheochromocytoma (19 of them suspected of this diagnosis on clinical grounds). The patients were separated into two groups: 15 with subnormal plasma conjugated NE + E, i.e., below 0.23 ng/ml (Group 1), and 23 patients above this limit (Group 2). Patients clinically suspected of pheochromocytoma represented 93% of the patients in Group 1 but only 21% in Group 2. Group 1 patients, compared to those of Group 2, had: 1) higher baseline plasma free NE + E (0.51 ± 0.07 ng/ml vs 0.30 ± 0.04 ng/ml,p < 0.02); 2) an increase in plasma free NE + E in response to stressful sampling (148% ± 59%, p < 0.05 vs 58% ± 30%), and a more pronounced response (p < 0.05) to glucagon administra- tion; 3) higher free NE + E and DA in the regional samples received during catheterization while conjugated NE and/or E were usually absent; and 4) a higher spread between maximum and minimum blood pressure and a higher maximum pulse rate recorded as well as the index of sympathotonia. All patients combined had the 'maximum pulse rate correlated negatively (p < 0.005) with conjugated NE + E, but positively (p < 0.005) with free NE + E. The clinical and biochemical similarity to pheochromocytoma was particularly striking in some Group 1 patients who had a selective defect in E conjugation; some of them had a history of surgical ex- ploration for the lesion, without result. The association of subnormal conjugated plasma NE and/or E with moderately elevated plasma NE + E and a more frequent pseudopheochromocytoma presentation may result from inadequate conjugation, and hence inactivation of NE and/or E. Excessive free catecholamines would account for the clinical symptoms and for tbe fact that the patients are well controlled by treatment with beta-adrenerglc blocking agents, either alone or in combination with a-blockers. Awareness of tbe existence of this variety of essential hypertension can obviate unnecessary surgery for wrongly suspected pheochromocytoma. (Hypertension 3: 347-355, 1981)