Moreover, in a second study in type 2 diabetes patients, using oral glucose tolerance test (OGTT) and isoglycaemic intravenous glucose infusions (IIGI), we analysed i) whether i.v. glucose per se could affect thyroid function parameters and ii) whether any changes could be elicited by infusion of the gastrointestinal hormones glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP1) and GLP2, which are known to be secreted after nutrient ingestion. Here, GIP is linked to type 2 diabetes mellitus.