A CORRELATIVE STUDY OF THE CARDIAC OUTPUT AND THE HEPATIC CIRCULATION IN HYPERTHYROIDISM 1

Abstract

The hepatic blood flow, measured in 14 hyperthyroidism subjects by the bromsul-phalein method, was found to be little, if at all, increased in spite of a definitely increased cardiac output. The splanchnic oxygen consumption (hepatic blood flow times the arterial-hepatic venous oxygen difference) was elevated even more than was the general metabolic rate. This increase was accomplished, in the face of the essentially normal splanchnic blood flow, by an increased oxygen extraction. The latter could easily result in anoxia of the centro-lobular zones of the liver and may well be related to the centro-lobular necrosis found in certain instances of complicated thyrotoxicosis. The ability of the liver to excrete bromsulphalein was moderately impaired in some, but not all, of the patients with hyperthyroidism. The hyperthyroidism was associated with an elevation of systolic and mean pressures, but not of diastolic pressures, in the right ventricle and pulmonary artery. These pressure elevations coexist with an elevated pulmonary blood flow (cardiac output) and a normal pulmonary peripheral vascular resistance. The cause of the pressure increases is not known; they do not appear to be related to left ventricular failure.