Hyperthyroidism: a secondary cause of isolated systolic hypertension.

Isolated systolic hypertension is the most common form of hypertension, especially among patients 50 years or older. What is not appreciated is that there are secondary causes of isolated systolic hypertension. Hyperthyroidism increases systolic blood pressure by decreasing systemic vascular resistance, increasing heart rate, and raising cardiac output. Potential cardiovascular consequences of hyperthyroidism include atrial arrhythmias (especially atrial fibrillation), pulmonary hypertension, left ventricular hypertrophy, and heart failure. The prevalence of hypertension is greater among hyperthyroid patients than euthyroid patients. Whether there is a blunted nocturnal decline in ambulatory blood pressure among hyperthyroid patients is more controversial. Treatment is associated with a reduction in systolic blood pressure, heart rate, and cardiac output.