Population survey of thyroid autoimmunity in Italy. Three year follow up.

Thyroid autoimmunity and primary hypothyroidism have been evaluated in a 3 year interval in 4 samples of general population from Bologna, Napoli, Palermo, Rome and Cagliari. The average prevalence of Mic-Abs was in males 4.1% and in females 10%. A significantly higher prevalence of Mic-Abs was found in the Cagliari sample where it reaches in males 6.1% and in females 20.4% (p less than 0.0005). Likewise Tg-Abs have been found increased in Cagliari (males: 4.6% vs 10.7%; females: 10.0% vs 16.6%; p less than 0.01). In the 3 year follow up Mic-Abs titre increases significantly whereas the Tg-Abs titre remains substantially unchanged. In the initial screening 1.65% of subjects were found to be latent (1.2%) or overt (0.45%) hypothyroids. Hypothyroidism was particularly frequent in the Cagliari sample and was constantly associated with Mic-Abs. In the 3 year follow up only 1 of 8 latent hypothyroids became overt.

Monoclonal autoantibody to thyroglobulin as a possible vector in immunodiagnosis and immunotherapy of differentiated thyroid cancer.

Differentiated thyroid carcinoma synthetize and secrete thyroglobulin. During its biosynthesis this antigen becomes expressed in the microvilli-bearing surface of carcinoma cells. Attempts have been carried out to target, with specific antithyroglobulin antibodies, the membrane bound absorption thyroglobulin in cancer cells for in vivo diagnosis and therapy. In the serum of patients with autoimmune thyroid diseases a high concentration of antithyroglobulin antibodies is frequently found (1-3 mg/ml). Their purification by immunoabsorption and dissociation is hampered by a low recovery and partial denaturation. It has been recently reported that about 1% of sera from Hashimoto's thyroiditis bear in their electrophoretogram a "myeloma-like protein". In the present report we describe in the serum of a Hashimoto patient a myeloma-like IgG which is an antithyroglobulin autoantibody with restricted functional and structural properties. The serum concentration of this myeloma-like IgG was found to be 40 mg/ml with a capacity of 6.5 nM of human thyroglobulin/mg IgG. The light chain composition was determined to be mostly of the lambda type. The clonal analysis of this myeloma IgG carried out by isoelectrofocusing, immunoblotting and autoradiography resulted in the recognition of several distinct clones, two of which were prominent at pH 8.7 and 7.8. By this technique and in view of the high serum concentration of this myeloma-like IgG, single clones of antithyroglobulin autoantibody can be easily obtained in high yields and without denaturation from human serum. This reagent could offer an ideal immunovector to target membrane-bound thyroglobulin of cancer cells.

Restricted clonality of antithyroglobulin antibodies in an M-component of Hashimoto's serum.

In serum of a 70 y. female with Hashimoto's thyroiditis we have identified an M-component IgG which is predominantly composed by a single class of antihuman thyroglobulin antibody. Our assumption is supported by Scatchard analysis and by the high concentration of lambda chains in serum and IgG fraction which are absorbed by h-thyroglobulin. Attempts to dissociate the monoclonal antibody treating the immunoprecipitate at acidic pH, were unsuccessful; only a few percent (3.7) of the antibodies could be released from immunoprecipitate and those were polyclonal. In order to explain the immunoprecipitating reaction of the monoclonal antibody, it is suggested that the antibody is reacting with a repetitive structure of the h-thyroglobulin molecule.

Hypothyroidism and thyroid autoimmunity in acute myocardial infarction (AMI).

It has been suggested that subjects with thyroid autoimmunity are more frequently affected by acute myocardial infarction (AMI), than the general population (Lancet ii, 155-158, 1977). Serum thyroid antibodies (microsomal and thyroglobulin) were measured in a cohort of 132 males admitted consecutively to the Coronary Unit of Clinica Medica II Univ. "La Sapienza" of Rome with AMI. In the AMI group the thyroid autoimmunity was twice as frequent as in an age matched random population (9.1 vs 17.4%), but the association was statistically weak (p less than 0.05). In the group over 60 y two cases of overt hypothyroidism were found and none in the control group. The prevalence of 2.5% is higher than that reported in previous surveys carried out in elderly populations. No differences have been demonstrated in concentration of serum cholesterol, triglycerides, apolipoprotein A and B between patients with and without thyroid autoimmunity, although the serum cholesterol of AMI patients and those with asymptomatic thyroiditis was significantly higher than that of the general population. It is concluded that the prevalence of thyroid autoimmunity and hypothyroidism are increased in AMI and migth thus contribute to development of hypercholesterolemia and/or immune mechanisms.

Low prevalence of thyroid antibodies in a Somalian population.

Prevalence rates of serum thyroid antibodies in a Somalian population have been compared with those of an Italian population. Thyroid antibodies have been evaluated by passive haemagglutination (microsomal antigen) and by 125I-thyroglobulin binding. In the Italian survey 13% of all subjects were positive for thyroid antibodies. A significantly lower prevalence of thyroid antibody positive subjects was found in the Somalian group (2,07%, P less than 0.001). It is suggested that the observed difference between Somalian and Italian populations could reflect nutritional or genetic causes which influence the antithyroid autoimmune response.