Association of Hypertension and Hyperthyroidism in a Subspecialty Clinic and a National Database

Objective Hypertension can cause significant morbidity and reduced life expectancy. Most patients with hypertension have primary hypertension; however, 10% to 15% have secondary hypertension. Endocrine disorders as a secondary cause occur in approximately 10% of patients with secondary hypertension, and thyroid disorders account for approximately 1% of all patients with hypertension. The identification of patients with hyperthyroidism has important benefits for these particular patients. The objective of this study was to examine the occurrence of high blood pressure in patients with hyperthyroidism. Methods We reviewed the clinical information available from 414 new patients referred to an endocrinology clinic in west Texas for evaluation of hyperthyroidism. The final cohort included 96 patients who had both thyroid laboratory tests and blood pressure measurements at the time of their clinic visit. We also examined this relationship in a nationally representative sample of US adults (National Health and Nutrition Examination Survey 2007-2012), which included thyroid test results and at least one blood pressure measurement (N = 8837). Results Sixty-five of these clinic patients had elevated blood pressure based on criteria suggested by the American College of Cardiology/American Heart Association. These patients had similar thyroid hormone levels as patients who did not have hypertension but tended to be older. Ordinary least squares regression analysis of the National Health and Nutrition Examination Survey 2007-2012 data demonstrated a significant positive association between free T3 levels and systolic blood pressure, adjusting for age, sex, and the use of levothyroxine. Conclusions These findings from a specialty clinic and a national sample suggest that clinicians should consider the possibility of hyperthyroidism in patients with hypertension, even in older patients.