CONTROL OF THYROID-CELL PROLIFERATION AND GOITROGENESIS

Human thyroid cells proliferate during development and in adults in response to physiologic and pathologic stimuli. Under normal conditions, they turn over about once every 8 years. The main physiologic regulators are thyrotropin and iodide and, in disease, thyroid-stimulating and thyroid-blocking antibodies. Growth factors modulate proliferation in vitro, but their role in vivo is still unknown. Mitogenic effects are mediated via three major pathways: the cyclic AMP, protein tyrosine kinase, and the Ca2+ phosphatidylinositol cascades. In this review, the role of these cascades in hyperthyroidism, congenital thyroid defects, and autonomous adenoma is analyzed 1.