Cell Differentiation; Insulin/metabolism; Signal Transduction; Thyroid Gland/metabolism; Thyrotropin/metabolism; Tissue Plasminogen Activator/metabolism; Urokinase-Type Plasminogen Activator/metabolism; Adenylyl Cyclases/metabolism; Aprotinin/pharmacology; Cell Differentiation/drug effects; Cells, Cultured; Colforsin/pharmacology; Cyclic AMP/metabolism; Dose-Response Relationship, Drug; Enzyme Activators/pharmacology; Epidermal Growth Factor/metabolism; Fibroblast Growth Factors/metabolism; Flavonoids/pharmacology; Humans; Indoles/pharmacology; Insulin/pharmacology; Iodine/metabolism; Iodine Radioisotopes; Maleimides/pharmacology; Mesylates/pharmacology; Mitogen-Activated Protein Kinase 1/antagonists & inhibitors; Mitogen-Activated Protein Kinase 1/metabolism; Mitogen-Activated Protein Kinase 3/antagonists & inhibitors; Mitogen-Activated Protein Kinase 3/metabolism; Plasminogen Inactivators/genetics; Plasminogen Inactivators/metabolism; Protein Kinase C/antagonists & inhibitors; Protein Kinase C/metabolism; Protein Kinase C beta; Protein Kinase Inhibitors/pharmacology; Pyrroles/pharmacology; RNA, Messenger/metabolism; Serine Proteinase Inhibitors/pharmacology; Signal Transduction/drug effects; Tetradecanoylphorbol Acetate/pharmacology; Thyroid Gland/cytology; Thyroid Gland/drug effects; Thyroid Gland/enzymology; Thyrotropin/pharmacology; Time Factors; Tissue Plasminogen Activator/antagonists & inhibitors; Tissue Plasminogen Activator/genetics; Urokinase-Type Plasminogen Activator/antagonists & inhibitors; Urokinase-Type Plasminogen Activator/genetics