Thyroid Research Thyroid Research Archive Hypothyroidism

Thyroxine alone may reverse hypertension in some patients with hypothyroidism

(July 2002)

The background of the study. Some patients with hypothyroidism have hypertension. This study evaluated the pathogenesis of hypertension in patients with hypothyroidism, and the extent to which it decreased during treatment with thyroxine (T4) and combined T4 and calcium-channel antagonist drug therapy (felodipine).

How the study was done. The main study group consisted of 30 patients with hypothyroidism (mean serum thyrotropin [TSH] concentration, 81 mU/L) and hypertension (mean blood pressure, 160/109 mm Hg). Other study groups (all age- and sex-matched) were 15 patients with hypothyroidism (mean serum TSH concentration, 81 mU/L) and normal blood pressure (mean, 121/86 mm Hg), 15 patients with hypertension (mean blood pressure, 155/108 mm Hg) and normal thyroid function, and 30 normal subjects (mean blood pressure, 125/78 mm Hg).

Blood pressure was measured at base line in all study subjects, after treatment with T4 in the two groups of patients with hypothyroidism, after treatment with felodipine in the patients with hypertension, and also after the addition of felodipine in the 15 patients with hypothyroidism and hypertension who remained hypertensive during T4 therapy.

The results of the study. As compared with the normal subjects, the patients with hypothyroidism and hypertension and those with hypothyroidism alone had a lower heart rate and increased vascular resistance to blood flow. The patients with hypertension alone also had increased vascular resistance. The changes were reversed during T4 or felodipine therapy, respectively, in the latter two groups.

Among the 30 patients with hypothyroidism and hypertension, 15 had normal blood pressure during T4 therapy (mean blood pressure, 118/83 mm Hg). The other 15 patients had persistent hypertension during T4 therapy (mean blood pressure, 151/105 mm Hg), and all 15 had normal blood pressure after felodipine therapy was added (mean, 114/83 mm Hg).

The conclusions of the study. Patients with hypothyroidism, especially those with hypertension, have increased vascular resistance, which may be reversed by T4 therapy.

The original article. Dernellis J, Panaretou M. Effects of thyroid replacement therapy on arterial blood pressure in patients with hypertension and hypothyroidism. Am Heart J 2002;143:718-24.