Spot 14 (S14) is a protein involved in fatty acid synthesis and was shown to be induced by thyroid hormone in rat liver. However, the presence of S14 in human serum and its relations with thyroid function status have not been investigated.The objectives of this study were to compare serum S14 concentrations in patients with hyperthyroidism or euthyroidism and to evaluate the associations between serum S14 and free thyroxine (fT4) or thyroid-stimulating hormone (TSH) levels.We set up an immunoassay for human serum S14 concentrations and compared its levels between hyperthyroid and euthyroid subjects. Twenty-six hyperthyroid patients and 29 euthyroid individuals were recruited. Data of all patients were pooled for the analysis of the associations between the levels of S14 and fT4, TSH, or quartile of TSH.The hyperthyroid patients had significantly higher serum S14 levels than the euthyroid subjects (median [Q1, Q3]: 975 [669, 1612] ng/mL vs 436 [347, 638] ng/mL, P < 0.001). In univariate linear regression, the log-transformed S14 level (logS14) was positively associated with fT4 but negatively associated with creatinine (Cre), total cholesterol (T-C), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and TSH. The positive associations between logS14 and fT4 and the negative associations between logS14 and Cre, TG, T-C, or TSH remained significant after adjustment with sex and age. These associations were prominent in females but not in males. The logS14 levels were negatively associated with the TSH levels grouped by quartile (ß = −0.3020, P < 0.001). The association between logS14 and TSH quartile persisted after adjustment with sex and age (ß = −0.2828, P = 0.001). In stepwise multivariate regression analysis, only TSH grouped by quartile remained significantly associated with logS14 level.We developed an ELISA to measure serum S14 levels in human. Female patients with hyperthyroidism had higher serum S14 levels than the female subjects with euthyroidism. The serum logS14 concentrations were negatively associated with TSH levels. Changes of serum S14 level in the whole thyroid function spectrum deserve further investigation.

Adipocyte fatty acid-binding protein (AFABP) has been shown to be a biomarker of body weight change and atherosclerosis. Changes in thyroid function are associated with changes in body weight and risks of cardiovascular diseases. The association between AFABP and thyroid function status has been seldom evaluated.The aim of this study was to compare the serum AFABP concentrations in hyperthyroid patients and those in euthyroid individuals, and to evaluate the associations between serum AFABP and free thyroxine (fT4) levels.For this study, 30 hyperthyroid patients and 30 euthyroid individuals at a referral medical center were recruited. The patients with hyperthyroidism were treated with antithyroid regimens as clinically indicated. No medication was given to the euthyroid individuals. The body weight, body mass index, thyroid function, serum levels of AFABP, and biochemical data of both groups at baseline and at the 6th month were compared. Associations between AFABP and fT4 levels were also analyzed.At the baseline, the hyperthyroid patients had significantly higher serum AFABP levels than the euthyroid individuals (median [Q1, Q3]: 22.8 [19.4, 30.6] ng/mL vs 18.6 [15.3, 23.2] ng/mL; P = 0.038). With the antithyroid regimens, the AFABP serum levels of the hyperthyroid patients decreased to 16.6 (15.0, 23.9) ng/mL at the 6th month. No difference in the AFABP level was found between the hyperthyroid and the euthyroid groups at the 6th month. At baseline, sex (female vs male, ß = 7.65, P = 0.022) and fT4 level (ß = 2.51, P = 0.018) were significantly associated with AFABP levels in the univariate regression analysis. At the 6th month, sex and fT4 level (ß = 8.09, P < 0.001 and ß = 3.61, P = 0.005, respectively) were also significantly associated with AFABP levels. The associations between sex and fT4 level with AFABP levels remained significant in the stepwise multivariate regression analysis, both at baseline and at the 6th month.The patients with hyperthyroidism had higher serum AFABP levels than the individuals with euthyroidism. In the patients with hyperthyroidism, the serum AFABP concentrations decreased after the antithyroid treatment. In this study, the serum AFABP concentrations were positively associated with female sex and the serum fT4 level.

Follistatin is a glycoprotein with various biologic functions that plays a role in adipocyte differentiation, muscle stimulation, anti-inflammation, and energy homeostasis. Thyroid hormones influence energy expenditure, glucose, and lipid metabolism. The association between serum follistatin level and thyroid function statuses has seldom been evaluated.The objectives of this study were to compare serum follistatin concentrations in different thyroid function statuses and to evaluate the associations between serum follistatin and free thyroxine (fT4) levels.In this study, 30 patients with hyperthyroidism (HY group) and 30 euthyroid individuals (EU group) were recruited. The patients of HY group were treated with antithyroid regimens as clinically indicated, whereas no medication was given to EU group. The demographic and anthropometric characteristics, biochemical data, serum levels of follistatin, and thyroid function of both groups at baseline and at the 6th month were compared. Data of all patients were pooled for the analysis of the associations between the levels of follistatin and fT4.At baseline, the HY group had significantly higher serum follistatin levels than the EU group (median [Q1, Q3]: 1.81 [1.33, 2.78] vs 1.13 [0.39, 1.45] ng/mL, P < 0.001). When treated with antithyroid regimens, the follistatin serum levels in HY group decreased to 1.54 [1.00, 1.88] ng/mL at the 6th month. In all patients, the serum levels of follistatin were positively associated with fT4 levels at baseline (β = 0.54, P = 0.005) and at the 6th month (β = 0.59, P < 0.001). The association between follistatin and fT4 levels remained significant in the stepwise multivariate regression analysis, both initially and at the 6th month.In comparison to the EU group, patients with hyperthyroidism had higher serum follistatin levels, which decreased after receiving antithyroid treatment. In addition, the serum follistatin concentrations were positively associated with serum fT4 levels in patients with hyperthyroidism or euthyroidism.