Thyroid Research Thyroid Research Archive Thyroid Disease

Mild hypertension is a feature of subclinical hyperthyroidism but not subclinical hypothyroidism

(November 2006)

The background of the study. Patients with hyperthyroidism or hypothyroidism may have increases in systolic and diastolic blood pressure, respectively. In this study, blood pressure was measured in subjects with subclinical hyperthyroidism and subclinical hypothyroidism.

How the study was done. The study subjects were subjects (mean age, 50 years) living in rural Australia in whom blood pressure and serum thyrotropin (TSH) and free thyroxine (T4) were measured.

The results of the study. There were 35 subjects (2.1 percent) with subclinical hyperthyroidism (low serum TSH, normal free T4) and 82 (4.8 percent) with subclinical hypothyroidism (high serum TSH, normal free T4); 1591 (93.1 percent) were euthyroid. Subjects with hypertension were excluded.

The mean systolic, but not diastolic, blood pressure was higher in the subjects with subclinical hyperthyroidism (132 mm Hg) than in those who were euthyroid (126 mm Hg). In contrast, the value in the subjects with subclinical hypothyroidism was similar (131 mm Hg) to that in the euthyroid subjects.

The frequency of hypertension, defined as blood pressure > or = to140/ > or = to90 mm Hg or treatment for hypertension, was higher in the subjects with subclinical hyperthyroidism (29 percent) than in the euthyroid subjects (14 percent), but similar in the euthyroid subjects and the subjects with subclinical hypothyroidism.

The conclusions of the study. Systolic blood pressure and the frequency of hypertension are slightly higher in subjects with subclinical hyperthyroidism than in normal subjects, but not in subjects with subclinical hypothyroidism

The original article. Walsh JP, Bremner AP, Bulsara MK, O’Leary P, Leedman PJ, Feddema P, Michelangeli V. Subclinical thyroid dysfunction and blood pressure: a community-based study. Clin Endocrinol (Oxf) 2006;65:486-91.