THE EFFECT OF CERTAIN THYROXINE ANALOGUES ON THE SERUM LIPIDS IN HUMAN SUBJECTS

Abstract

SUMMARY: 1. Certain analogues of thyroxine have been administered to twenty-six hypothyroid patients and 132 euthyroid hypercholesterolaemic men with coronary heart disease. The analogues studied were d-thyroxine, 3:5:3′:5′-tetraiodothyroformic acid, 3:5:3′:5′-tetraiodothyronamine, 3:5:3′-triiodo-l-thyronine, 3:5:3′-triiodo-d-thyronine, 3:5:3′-triiodothyroacetic acid, 3:5-diiodo-l-thyronine, 3:5-diiodo-d-thyronine and 3:5-diiodothyroacetic acid. 2. In both hypothyroid and euthyroid patients, most of these analogues reduced the serum cholesterol without necessarily elevating the basal metabolic rate (b.m.r.). Nevertheless, in euthyroid patients with coronary heart disease several produced angina in the absence of any change in b.m.r. and this has been regarded as a sign of increased myocardial metabolism insufficient to be reflected in the overall measure of b.m.r. of all tissues. The possible differential effect of these analogues on the oxygen requirements of various tissues is discussed. 3. Although it has been possible to maintain low cholesterol levels for periods up to 3 months during the administration of several of these analogues, the dose required for this purpose was often so close to the dose which provoked angina that most cannot be recommended for widespread administration for the reduction of the hypercholesterolaemia frequently found in patients who have coronary heart disease. d-Thyroxine may prove to be an exception and requires further clinical assessment.