Elevated circulating Gpnmb levels are associated with hyperthyroidism

BACKGROUND: Glycoprotein non-metastatic protein B (Gpnmb) has been identified as a new cytokine secreted by hepatocyte that plays an important role in balancing lipid homeostasis and development of obesity and metabolic disorders. However, information is not available regarding the association between circulating Gpnmb and hyperthyroid in humans. METHODS: We measured serum Gpnmb in 180 hyperthyroid patients and 82 healthy subjects that were recruited from the clinic. Of them, 46 hyperthyroid patients received thionamide treatment for 3 months. RESULTS: Hyperthyroid subjects had higher levels of circulating Gpnmb than healthy controls (47.8 ± 10.1 ng/mL vs 31.0 ± 4.9 ng/mL, P < 0.001). Subjects with higher levels of serum free triiodothyronine (T3) and free thyroxine (T4) had higher levels of circulating Gpnmb. After thionamide treatment, levels of circulating Gpnmb in hyperthyroid subjects remarkably declined with significant improvement of thyroid function (P < 0.001). Furthermore, the change of circulating Gpnmb levels was significantly associated with basal metabolic rate (BMR) and thyroid hormones, including free T3 and free T4, adjusting for age, gender, smoking and BMI before thionamide treatment. In multivariable logistic regression analyses, circulating Gpnmb was significantly associated with risks of hyperthyroidism (OR (95% CI): 1.44 (1.20–1.74), P < 0.001), adjusted for age, gender, BMI, fasting glucose, HOMA-IR, LDL-cholesterol, ALT and AST. CONCLUSIONS: These findings indicate that circulating Gpnmb concentrations are independently associated with hyperthyroid, suggesting that circulating Gpnmb may be a predictor of risk for hyperthyroidism and can be used for therapeutic monitoring.