SUMMARY To study whether there is an association between hypertension and hypothyroidism, measurements of blood pressure and thyroid function were determined in 477 female patients with chronic thyroiditis. Based on the blood levels of thyroxine (T 4 ) and thyroid stimulating hormone (TSH), 308 patients were considered euthyroid and 169 were hypothyroid [T 4 = 2.9 ± 0.1 /xg/dl and TSH = 105.8 ± 6.8 /xU/ml (mean ± SEM)]. Diastolic, but not systolic, blood pressure in hypothyroid patients over 50 years was higher than in euthyroid patients of corresponding age groups. The prevalence of hypertension was higher in hypothyroid patients when hypertension was defined as the systolic and/or diastolic blood pressure above 160/95 mm Hg (14.8% vs 5.5%; p < 0.01). Correlations between diastolic, but not systolic, blood pressure and either the blood level of triiodothyronine (T 3 ) or T 4 was significant (r = -0.174, p < 0.01, and r = -0.208, p < 0.01, respectively) when data from both euthyroid and hypothyroid patients were combined. Adequate thyroid hormone replacement therapy for an average 14.8 months in 14 patients resulted in a normalization of thyroid function and a reduction of blood pressure (p < 0.01). In four who showed no change in thyroid function due to inadequate replacement therapy, blood pressure remained elevated. These results suggest a close association between hypertension and hypothyroidism. (Hypertension 5: 112-115, 1983) KEY WORDS • blood pressure chronic thyroiditis thyroid deficiency • thyroxine treatment H YPOTHYROIDISM is listed as a cause of secondary hypertension in some textbooks of hypertension; however, there appears to be less certainty about the prevalence of hypertension. For example, in Kaplan's Clinical Hypertension, the prevalence is reported as 26%,' and in Genest's Hypertension, Physiology and Treatment, the prevalence is reported as 50%.2 On the other hand, Skelton and Sonnenblick 3 have reported either low or normal blood pressure in this disorder. This report describes the relation of thyroid function and blood pressure, compares the age-related increase in blood pressure in euthyroid patients with that of hypothyroid patients, and assesses the effect of thyroid hormone replacement therapy on blood pressure in hypertensive hypothyroid patients. The results suggest a high prevalence of hypertension in hypothyroid patients over 50 years old.
Methods
Patient PopulationThis investigation involved 477 patients with chronic thyroiditis; they ranged in age from 20 to 69 years. They visited Ito Hospital between January 1980 and December 1980 and were seen by one of the authors. The diagnosis of chronic thyroiditis was based on the presence of goiter and the demonstration of circulating thyroid antibodies (microsomal and thyroglobulin). None had previously been treated for hypothyroidism or hypertension.To assess the degree of thyroid deficiency, these patients were divided according to the levels of serum thyroxine (T 4 ) and thyroid stimulating hormone (TSH) concentrations. Patients wi...