Comparative Effects of Thyroxin Analogues as Hypocholesteremic Agents

Abstract

L-thyroxin and four thyroxin analogues were administered to a group of hypercholesteremic euthyroid patients, the majority with arteriosclerotic heart disease, and the effects on serum total cholesterol compared. L-thyroxin and each of the analogues studied, tetraiodothyroformic acid, dimethyldiiodothyroformic acid, D-thyroxin and D-triiodothyronine, were given to four to nine patients for periods up to 10 months. At the doses employed each of the analogues resulted in a reduction in the mean level of serum cholesterol without obvious evidence of hypermetabolism or aggravation of angina pectoris or congestive heart failure. The reduced level of serum cholesterol was sustained throughout the period of hormone administration, and upon the substitution of a placebo returned to the pretreatment range. L-thyroxin, at the dose employed, also effected a modest sustained reduction in serum cholesterol but both patients with angina included in this group experienced an increase in severity of symptoms. Except for four patients who developed acneiform dermatitis, salivary gland swelling, or gastrointestinal symptoms during the administration of the formic acid analogues, no toxic or undesirable effects were observed from any of the analogues. To evaluate better the general metabolic effects of the analogues each was administered to three or more of a group of seven myxedematous patients for periods of 6 to 12 months. Given in sufficient amount all were observed to increase basal metabolic rate and to maintain a clinically euthyroid state. From these observations, it is concluded that the D-isomers of thyroxin and triiodothyronine, while not without general metabolic effects, are tolerated by the majority of euthyroid patients with coronary atherosclerosis in amounts sufficient to maintain a reduced serum cholesterol level.