TSH and biogenic amine signals in the regulation of thyroid function: independent regulation by protein kinase C and G proteins.

Abstract

The primary role of the thyroid cell is to synthesize and secrete the thyroid hormones, T3 and T4 (Dumont et al. 1971; Robbins et al. 1980). This must be accomplished in a regulated manner and despite a variable intake of iodine. This role must also be accomplished despite the fact that the synthesis and secretion of thyroid hormones involves numerous steps. These include 1) the uptake of iodide across the basal membrane of the cell in a scavanging and concentrative fashion; 2) efflux of iodide across the apical membrane into the follicular lumen of the thyroid follicle; 3) the synthesis of thyroglobulin and its vectorial transport to the site of iodide efflux; 4) iodination of thyroglobulin; 5) regulated storage of the iodinated thyroglobulin; 6) lysosomal targeting and biodegradation, of the iodinated thyroglobulin; and 7) ultimately, secretion of T3/T4 into the bloodstream, across the basal membrane