['Women with polycystic ovary syndrome (PCOS) mostly have profound insulin resistance (IR) and β-cell dysfunction. Although thioredoxin-interacting protein (TXNIP) is a major regulator in IR and insulin secretion, no data on the plasma TXNIP level in patients with PCOS are available. This study aimed to determine the plasma TXNIP level and discuss the relationship between TXNIP and β-cell dysfunction/IR in patients with PCOS.', 'Eighty-three women with PCOS and 52 controls.', 'Insulin sensitivity was expressed by M value obtained from euglycaemic-hyperinsulinaemic clamp. Homoeostatic model assessment for β-cell function (HOMA-β), △Ins30/△Glu30 and AUCins/glu were considered as the indices of fasting state, early-phase and total insulin secretion during oral glucose tolerance test, respectively. To evaluate β-cell function adjusted for insulin sensitivity, disposition index (DI) was used: basal DI (DI0), early-phase DI (DI30) and total DI (DI120). Plasma TXNIP levels were measured by enzyme-linked immunosorbent assay.', 'Case-control study.', 'Patients with PCOS had higher serum TXNIP, whereas lower M value, DI0, DI30 and DI120 than controls (P < 0·05); their TXNIP correlated positively with weight, waist-to-hip ratio (WHR), body mass index (BMI), Ins0, Ins120 and HOMA-β and correlated negatively with M value and DI120 (P < 0·05). Multiple stepwise regression analysis indicated that TXNIP remained associated with M value in PCOS subjects, after adjusting weight, BMI, WHR, HOMA-β, Ins0, Ins120 and DI120. However, no relationship between TXNIP and impaired β-cell function was found.'] Is elevated serum thioredoxin-interacting protein in women with polycystic ovary syndrome associated with insulin resistance?