One hundred and forty-two persons referred for assessment of thyroid function were studied in relation to their thyroid function and fasting serum lipids. Forty-five individuals, who had no family history of thyroid disease, were euthyroid, and were negative for thyroid antibodies formed the control group. The remaining 97 patients were fitted into six groups as follows--euthyroid Hashimoto's thyroiditis, thyroiditis with exagggerated TSH response to TRH, and four groups of increasing grades of thyroid failure based on the level of serum TSH. Only in the two most severely hypothyroid groups was cholesterol significantly elevated as compared with control levels. A graded increase in mean serum triglyceride, was observed as thyroid failure increased; however, values were not different (P greater than 0.05) from the control group. However, partial correlation analysis indicated that serum cholesterol was related to increasing levels of serum TSH and that this dependency was not influenced by age or weight. Although serum cholesterol was related to thyroid function in the study population, it was an insensitive indicator of the metabolic effects of thyroid hormone.

In 129 patients with Type 1 (insulin-dependent) diabetes mellitus, 100 healthy control subjects and 91 non-diabetic first degree relatives of Type 1 patients, we investigated variation in serum IgA, IgG and IgM concentrations with sex and HLA-B phenotype. Two patients with onset before the age of 15 years were completely IgA-deficient. One additional patient was completely IgG-deficient. Excluding these three cases, diabetic patients had serum IgA and IgM concentrations comparable to control subjects. IgG levels of patients were, however, significantly lower than those of control subjects (11.66 versus 12.69 g/l, p = 0.003). Non-diabetic first degree relatives of patients had IgG levels intermediate between those of diabetic patients and control subjects. There was some indication that IgA concentrations were lower in the 53 patients with HLA-B8 (1.91 versus 2.21 g/l, p = 0.038). No association was found between IgM or IgG levels and HLA phenotypes.

A chemiluminescence method was developed to measure thyroid peroxidase (TPO) activity and the inhibitory effect of anti-TPO antibodies in purified porcine TPO. The TPO preparation was characterized kinetically and controlled by Western-blotting technique. The chemiluminescence method proved to be reproducible and much more sensitive than the widely used guaiacol method, being able to detect TPO concentrations of 2.21 × 10−5 g/L vs 6.63 × 10−2g/L with the latter. Otherwise, the determinations with the two methods correlated well (r = 0.76). Investigating the effect of IgGs from 23 hypothyroid patients on measured TPO activity, we detected inhibition in 19 cases with the chemiluminescence technique (15 with the guaiacol method). Anti-TPO antibodies showed competitive inhibition of TPO activity with respect to the substrate guaiacol. In both systems, the inhibition is present in the IgG F(ab′)2 fragment. We conclude that the high sensitivity of chemiluminescence detection allows routine determination of the inhibition of TPO activity by anti-TPO antibodies.

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