As a newly emerging metabolic regulator, accumulating evidence suggests that the circulating fibroblast growth factor 19 (FGF19) level correlated with lipid and glucose metabolism. Several independent groups have found that FGF19 was highly likely associated with multiple metabolic disorders. Thyroid dysfunction is believed to be associated with metabolism diseases. However, to date, few studies have investigated the role of FGF19 in patients with thyroid dysfunctions. For this purpose, a cross-sectional study was done to estimate the role of FGF19 in patients with different thyroid functions. Compared with the healthy control, the present study revealed that serum FGF19 levels were significantly decreased in overt hypothyroidism patients (78.7 [52.7-121.2] vs 292.4 [210.2-426.5] pg/mL, P <0.001). FGF19 concentration was also lower in the subclinical hypothyroidism group than it was in the healthy control group (95.8 [71.7-126.3] vs 292.4 [210.2-426.5] pg/mL, P <0.001). However, there was no significant difference in FGF19 level between the isolated thyroid autoantibody positive group and the healthy control group (252.0 [205.9-353.5] vs 292.4 [210.2-426.5] pg/mL, P >0.05). Also, serum thyroid stimulating hormone (TSH) was an independent predictor of FGF19. In conclusion, thyroid insufficiency but not thyroid autoimmunity may have impacted serum FGF19 concentrations. As the role of FGF19 is becoming more and more important in the pathogenesis of many metabolic diseases, we proposed that the thyroid hormone level should be taken into account when the serum concentration is explained. Further studies are needed to elucidate the role of FGF19 in the development of hypothyroidism.