Hyperthyroidism and Demonstration of Circulating Long-Acting Thyroid Stimulator Following Hypophysectomy for Chromophobe Adenoma

Abstract

The case is described of a 44-yrold woman in whom hyperthyroidism developed 6 months after (subtotal) hypophysectomy and pituitary irradiation for a chromophobe adenoma. Long-acting thyroid stimulator (LATS) bio-assay revealed the presence of a circulating thyroid activator which effected maximal murine thyroidal ¹³¹I release at 2 hr, although blood radioactivity did not decline significantly thereafter. Since thyroid-stimulating activity was confined to the immunoglobulin G (IgG) fraction of plasma and was neutralized on incubation with antiserum to human IgG, while radioimmunoassay revealed no detectable circulating thyrotropin, characterization of this thyroid activator as LATS appears warranted. Pituitary-thyroid relationships in Graves' disease and the roles of TSH and LATS in this disorder are discussed.