[Thyroid microsomal autoantibodies in thyroid disease: their value as an antigenic marker]

An autoimmune disease can be the cause of thyroid disfunction. Determination of autoantibodies titers is the best way of demonstrating its existence. We studied 172 thyroid patients (146 females, 26 males) with ages ranging from 15 to 81 years. Thyroid microsomal autoantibodies (TMA) were detected by a modified agglutination test (SERA-TEK kit, Ames Div); a dilution greater than or equal to 1/1600 was considered as diagnostic of autoimmune disease. Patients were classified according to morphological and functional status in 3 groups: GI = non toxic goiter, n = 98 (71 diffuse, 20 multi and 7 uninodular); GII = toxic goiter, n = 62 (52 diffuse, 4 multi, 2 uninodular and 4 subacute thyroiditis); G III = hypothyroidism, n = 12 (5 primary hypothyroidism and 7 chronic thyroiditis). A control group of 30 normal individuals, ages ranging from 19 to 85 years was also studied. Diagnostic titers of TMA were found in 30.8% of group I, 88.5% of group II, 91.6% of group III and only in 6.6% of controls. The high incidence of positive TMA in toxic diffuse goiter (96.1%) as well as in hypothyroid patients was expected since these are typical examples of thyroid autoimmune disease. In the non toxic goiter group, positive TMA were present in 50% of multinodular, 28% of uninodular and 25% of diffuse goiters and the incidence of positive TMA varied according to age, being higher over the age of 40 years and lower under the age of 20 years. We postulate that this unexpected high incidence of positive TMA in non toxic goiter is due to amelioration of chronic iodine deficiency inducing the expression of latent autoimmune disease.(ABSTRACT TRUNCATED AT 250 WORDS)