Growth factors and goitrogenesis

By combining data front studies of multinodular non-toxic goitre (MNTG) wit h data from rat models of goitre induction and in vitro models, a map of th e growth factors involved in goitrogenesis has been constructed. We have ad dressed the roles of the insulin-like growth factors, transforming growth f actors, fibroblast growth factors, endothelins, etc. We hypothesise that an imbalance in the interactions between the various growth factor axes exist s in MNTG which favours cell replication. Thyrotrophin, although not signif icantly elevated in MNTG, exerts critical effects through interactions with autocrine and paracrine factors and their receptors. Expansion of the thyr oidal vascular bed through angiogenesis is closely co-ordinated with follic ular cell expansion and folliculo-neogenesis, and while the integrated para crime actions of fibroblast growth factors, vascular endothelial growth fac tor and endothelin probably play central roles, additional, as yet elusive, factors are probably involved. The combination of in vitro and in vivo app roaches, designed to address specific questions, will undoubtedly continue to prove invaluable in dissecting further the complex inter actions that ex ist between these growth factors, their binding proteins and receptors in g oitrogenesis.