Decreased circulating levels of ANGPTL8 in Graves’ disease patients

BACKGROUND: Angiopoietin-like protein 8 (ANGPTL8), a newly identified hormone, has been recently characterized as a metabolic regulator which can affect energy homeostasis and has interesting potentials as a metabolic disease therapy. However, little is as yet known as to whether circulating ANGPTL8 levels are altered in thyroid dysfunction. This study measured serum ANGPTL8 levels in patients with Graves' disease and explored the correlations between its serum levels and thyroid index in Graves' disease. METHODS: The concentration of ANGPTL8 was analyzed in blood samples of 128 well-characterized individuals whose anthropometric parameters, biochemical parameters, and thyroid index were measured. The participants were divided into Graves' disease patients (n = 60) and healthy control subjects (n = 68). Logistic regression was used to evaluate the relationship between ANGPTL8 and Graves' disease. RESULTS: Serum ANGPTL8 levels were more significantly decreased in Graves' disease patients than in healthy control subjects (177.67 ± 135.07 vs 326.41 ± 194.72 pg/mL; p < 0.001). Serum ANGPTL8 was negatively correlated with free triiodothyronine (FT3), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOAb) while being positively correlated with thyrotropin (TSH). Logistic regression analyses demonstrated that serum ANGPTL8 was significantly associated with Graves' disease (p < 0.05). CONCLUSIONS: Circulating concentrations of ANGPTL8 showed a significant reduction in Graves' disease patients. Thus, it is suggested that thyroid function should be taken into consideration when evaluating the results of ANGPTL8.