Since hyperthyroidism is a general disease in which one of the most fundamental physiologic processes of the body is abnormally accelerated, it influences organic functions generally. The changes in vascular tonus and the increase in cardiac output and in velocity of blood flow are usually reflected in some alterations of blood pressure. In the characteristic case, the systolic pressure shows a slight to moderate elevation while the diastolic pressure remains relatively unchanged or is slightly lowered, resulting in an increase of pulse pressure. That these changes represent physiologic responses to the disease is indicated by the fact that the pressures assume their previous normal levels with remission of the metabolic rate to a normal basal level.
There are, however, cases in which the systolic pressure is higher than that occurring in the kind of case just indicated or in which both the systolic and the diastolic pressure are considerably elevated.