title: Incidence of antibodies blocking thyrotropin effect in vitro in patients with euthyroid or hypothyroid autoimmune thyroiditis.
abstract: Autoantibodies blocking the TSH-dependent production of cAMP in thyroid cells (TSH-BAb) have been described in atrophic thyroiditis (AT; idiopathic myxedema) and in neonates with transient hypothyroidism, but their incidence in autoimmune thyroiditis in relation to thyroid status remains to be completely established. To this purpose TSH-BAb were evaluated in a group of 140 consecutive patients with autoimmune thyroiditis, which included 26 cases of AT and 114 subjects with goitrous Hashimoto's thyroiditis (HT); among the goitrous group 27 were euthyroid (HT-E), 32 had subclinical hypothyroidism (HT-SH), and 55 had clinical hypothyroidism (HT-H). TSH-BAb were measured in immunoglobulin G prepared by DEAE-Sephadex A-50 by determining their ability to inhibit TSH-dependent cAMP production in a differentiated strain of cultured rat thyroid cells (FRTL-5). Using this sensitive and reproducible method, TSH-BAb were detected in 12 of 26 (46%) patients with AT, in 1 of 27 (3.7%) subjects with HT-E, in 3 of 32 (9.4%) with HT-SH, and in 20 of 55 (36%) with HT-H. The prevalence of TSH-BAb was higher in AT vs. HT-H (P less than 0.001), HT-SH (P less than 0.001), or HT-E (P less than 0.001), and in HT-H vs. HT-SH (P less than 0.001) or HT-E (P less than 0.001). Mean TSH-BAb levels in AT were higher than those in HT-H (P less than 0.005) and HT-SH (P less than 0.025); the difference was not significant between HT-H and HT-SH. An inverse correlation was found between TSH-BAb levels and estimated goiter weight (P less than 0.005). The results of the present study indicate that 1) in autoimmune thyroiditis TSH-BAb are detectable almost exclusively in hypothyroid patients, their prevalence being higher in overt hypothyroidism than in subclinical thyroid failure; 2) the prevalence of TSH-BAb and their mean levels are higher in hypothyroid patients with AT than in those with HT; and 3) therefore, the presence of circulating TSH-BAb appears to be related to the development of hypothyroidism and thyroid atrophy.
authors.affiliation: Cattedra di Endocrinologia e Medicina Costituzionale, University of Pisa, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Chiovato
authors.forename: P
authors.initials: P
authors.lastname: Vitti
authors.forename: F
authors.initials: F
authors.lastname: Santini
authors.forename: G
authors.initials: G
authors.lastname: Lopez
authors.forename: C
authors.initials: C
authors.lastname: Mammoli
authors.forename: P
authors.initials: P
authors.lastname: Bassi
authors.forename: L
authors.initials: L
authors.lastname: Giusti
authors.forename: M
authors.initials: M
authors.lastname: Tonacchera
authors.forename: G
authors.initials: G
authors.lastname: Fenzi
authors.forename: A
authors.initials: A
authors.lastname: Pinchera
mesh_terms: D000328:Adult; D000818:Animals; D000906:Antibodies / Q000032:analysis*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000209:etiology / Q000276:immunology* / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D013967:Thyroiditis, Autoimmune / Q000150:complications / Q000276:immunology* / Q000378:metabolism; D013972:Thyrotropin / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000906:Antibodies; D013972:Thyrotropin; D000242:Cyclic AMP