Summary:This study aimed at evaluating the frequency of autoimmune disorders in Addison's disease. We have observed 180 patients (113 females, 67 males, aged 9-74 years) for 1 to 26 years. Tuberculosis was noted in 54 patients. Autoimmune disorders were found in 80 patients (44%); however, 125 (69%) patients were believed to have an autoimmune origin of adrenocortical insufficiency. In 20 patients two or more autoimmune disorders were found to coexist with Addison's disease.

The origin of the isolated secondary adrenal insufficiency is unknown in most cases. An observation of a group of over 100 patients with secondary adrenal insufficiency and coexisting autoimmune abnormalities suggests that autoimmunity could be a frequent cause of idiopathic secondary failure, similarly as in Addison's disease. We studied 176 patients with idiopathic isolated secondary adrenal insufficiency. The methods included clinical examination and measurements of pituitary, adrenal, thyroid and gonadal hormones in all the cases. Since thyroid autoimmunity has been the most frequent finding in Addison's disease we have also chosen thyroid autoantibodies as markers of an autoimmune process in our material. Anti-peroxidase, anti-microsomal and anti-thyroglobulin autoantibodies were determined in 151 patients. In 111 out of 151 patients (73%) coexisting autoimmune diseases and/or presence of thyroid autoantibodies were detected. The most frequent autoimmune diseases associated with secondary adrenal insufficiency were primary hypothyroidism, hyperthyroidism (mainly in the past) and premature ovarian failure. Thyroid autoantibodies, especially antiperoxidase autoantibodies, were present in 106 patients. Thus, coexistence of isolated secondary adrenal insufficiency with some autoimmune disorders in 73% of the patients under study suggests that autoimmunity is the most frequent cause of the idiopathic form of this disease.

The co-existence of autoimmune disorders with secondary adrenal insufficiency suggests an autoimmune aetiology for the ACTH deficiency.

We have determined the incidence of autoimmune thyroid disorders in patients with Addison's disease. The material comprised 212 patients, 128 women and 84 men, aged 9-74 years. In 58 patients tuberculosis and in six patients other adrenal disorders were diagnosed. In the remaining 148 patients the auto-immune mechanism was the most probable cause of adrenocrotical insufficiency. In order to evaluate the thyroid abnormalities seen in patients with Addison's disease the T3, T4 (RIA), TSH (ELISA) and anti-thyroid autoantibodies were determined apart from routine clinical examination. Antimicrosomal, anti-thyroglobulin and anti-thyroperoxidase antibodies were measured in 91, 188 and 81 cases respectively. Thyrotoxicosis was diagnosed in 17 and primary hypothyroidism in 18 cases. Moreover, eight patients had evidence of subclinical hypothyroidism. The anti-thyroglobulin antibodies with titer ranging from 1:80 to 1:10,000 were detected in 66 patients, whereas antimicrosomal antibodies were found in 51 patients at a titer ranging from 1:80 to 1:9720. Autoantibodies against thyroid peroxidase were found in sera of 67 patients, with titer ranging from 1:2000 to 1:25,6000.

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