Reversible hypertension and hypothyroidism.

Six patients with hypothyroidism and hypertension whose blood pressure fell to normal when treated with thyroxine (172 +/- 7.2/112 +/- 2.1 to 140 +/- 3.2/84+/- 1.6 mmHg, P < 0.001) are described. Plasma renin activity (1.76 +/- 0.63 ng angiotensin I.ml-1.h-1) was low before treatment. Hypertension with low plasma renin is consistent with sodium retention. Hypertension in the hypothyroid patient only requires further evaluation if it persists after adequate treatment with thyroxine.