Protein composition in single follicles, homogenates and fine-needle aspiration biopsies from normal and diseased human thyroid

Abstract

Abstract. The protein composition of the thyroid colloid was analysed by microgel electrophoresis and densitometry in 41 euthyroid patients. The colloid samples were obtained from single follicles by micropuncture, from homogenates of microbiopsies or from aspiration biopsies. Fourteen of the patients had morphologically normal thyroid tissue, 18 had atoxic nodular goitre and 9 of the patients had atoxic adenoma. Ten of the patients with nodular goitre had prior to the investigation recieved lithium therapy for psychiatric disorders. The main component of the thyroid colloid was 19S thyroglobulin (TG), but larger iodoproteins (S-TG) and smaller protein fractions, an albumin-like protein and a pre-albumin fraction, were also present in varying relative amounts. Analyses of homogenates of microbiopsies from normal thyroid tissue demonstrated the same protein composition as observed in single follicles. In colloid samples from atoxic nodular goitre the lighter protein fractions were absent in most of the samples. Analyses of homogenates or aspiration biopsies could not demonstrate this alteration in the protein composition in nodular goitre. Lithium therapy resulted in a significantly lower amount of the lighter protein fractions but unchanged amounts of the globulin fractions in atoxic nodular goitre. In the atoxic adenomas the protein composition was heterogeneous. The major globulin fractions as well as the lighter protein fractions were present in the analyses of colloids and homogenates of microbiopsies. Aspiration biopsies from atoxic adenomas could not be used for analyses of the protein composition due to contamination with serum proteins.