Many clinically euthyroid patients with severe, chronic, non-throidal illnesses (i.e. sick euthyroid patients) have very low circulating concentrations of total and absolute free triiodothyronine (T3), low-normal concentrations of total thyroxine (T4), elevated concentrations of absolute free T4, and circulating concentrations of thyrotrophin (TSH) that are either normal or subnormal. This study was undertaken to elucidate the mechanism of the low circulating T3 concentrations. The disappearance rate of 125 I-T3 from the circulation of five representative sick euthyroid patients was studied and found to be slower, but not significantly so, compared with three control subjects, thus excluding an increased destruction rate as the cause of the low T3 levels. A selective decrease of T3 secretion from the thyroid gland of these patients was also excluded by the results of TSH stimulation tests. Inhibition of extra-thyroidal conversion of T4 to T3 was suggested by studies of the thyroid function in a hypothyroid woman with a Grade IV lymphoma on T4 replacement therapy. When the lymphoma was in remission, her circulating T3 concentration was 2-55 nmol/l but when it relapsed it fell to 0-55 nmol/l. The T4 concentrations were 124-7 nmol/l and 126 nmol/1 respectively. Decreased monodeiodination of T4 to T3 in sick euthyroid patients was confirmed by paper chromatography of extracted serum obtained 48 h after an i.v. injection of 125 I-T4 into two severely ill patients from the intensive therapy unit and a control subject. Peaks of radioactivity corresponding to 125 I-T4 and 125 I-T3 were detected in the control subject, but only a single peak corresponding to 125 I-T4 was detected in the ill patients.

Plasma free fatty acid levels in acute myocardial infarction in diabetic and non-diabetic patients Acute myocardial infarction carries a high mortality among patients suffering from diabetes mellitus and there is a suggestion that the risk of cardiovascular death may be increased by the use of hypoglycaemic drugs'. A high incidence of primary ventricular fibrillation among those previously on oral hypoglycaemic drugs has also been found2.As raised plasma free fatty acids (FFA) have been implicated in the genesis of cardiac arrhythmnias3, we considered that this may be the mechanism in diabetics, who are known to have impairment of the normal fall in FFA levels after glucose ingestion after myocardial infarction4.We therefore decided to investigate the relation between the incidence of ventricular fibrillation among diabetic patients admitted with acute myocardial infarction and the levels of circulating FFA and to compare the findings with those observed in non-diabetic people. Patients, methods, and resultsTwenty-three diabetic and 24 non-diabetic patients with proved myocardial infarction within the previous 30 hours were studied. Twelve of the diabetics were women whereas there were only two women among the non-diabetics. The mean age of the diabetic patients was significantly higher than that of the non-diabetics, but the ages of the orally treated and insulintreated diabetics were similar. The insulin-treated group had had diabetes longer than the tablet-treated patients (15 years and 6-1 years respectively.) A venous blood sample was taken from each patient on admission, which was a mean of 6-57 hours after the onset of chest pain in the non-diabetic patients and 9-9 hours in the diabetics. The plasma sugar was measured and FFA levels estimated using a modification of the method of Dole and Meinertz,5 substituting tetra-n-buLtyl ammonium hydroxide as titrant. Serum albumin was also measured within 24 hours.Initial plasma sugar concentrations were significantly higher among the diabetic than among the non-diabetic patients (P<0 0005), but no difference emerged between the two groups in FFA levels. There was also no significant difference in circulating FFA between those patients on oral drug treatment and those receiving insulin. Ten patients, five in each group, developed primary ventricular fibrillation. No difference was detected in the corresponding FFA levels between patients who developed this arrhythmia and those who did not, either when the results were analysed as a whole or when the diabetics were considered separately. In eight of these 10 patients, the blood sample was taken within one and a half hours of the occurence of the arrhythmia.Nine of the 47 patients died in hospital. Seven of these were diabetics, of whom five were on insulin. Serum albumin was lower in the diabetics than in the non-diabetics (P<0-01). Three newly diagnosed diabetics and three on diet alone were included in the study. They had an uncomplicated progress. DiscussionThe diabetic population showed the high proportion of w...