Objective: To investigate the association between plasma transthyretin levels and risk of newly diagnosed type 2 diabetes mellitus (T2DM) and impaired glucose regulation (IGR) in a Chinese population. Design: We performed a case-control study, including 1,244 newly diagnosed T2DM patients, 837 newly diagnosed IGR patients, and 1,244 individuals with normal glucose tolerance (NGT). The diagnostic criteria were recommended by World Health Organization in 1999. All cases were recruited from patients who, for the first time, received a diagnosis of T2DM in the Department of Endocrinology, Tongji Hospital, Tongji Medical College, Wuhan, China, from December 2010 to December 2016. Concomitantly, general population undergoing a routine health checkup in the same hospital were enrolled as controls. The inclusion criteria were age ≥ 30 years, BMI < 40 kg/m2, and no history of diagnosis of diabetes or receiving pharmacological treatment for hypertension and hyperlipidemia. Participants with clinically significant neurological, endocrinological, psychological or other systemic diseases, as well as acute illness or chronic inflammatory or infectious diseases, were excluded from the present study. Written informed consent was obtained from each participant. Besides, cases were stringently matched to controls in a 1:1 ratio, based on sex and age (± 3 years). All participants enrolled were of Han ethnicity, and gave a commitment of taking no medication known affecting glucose tolerance or insulin secretion before participating in the study. Fasting blood samples were collected in EDTA-anticoagulative tubes and separated for plasma within 1 h. Then plasma was kept at -80℃ prior to analyses. Plasma transthyretin levels were measured by BS 200 Autoanalyser (Mindray, Shenzhen, China) using immunoturbidimetric method.