Levels of sST2 and NT-proBNP biomarkers in patients with acute coronary syndrome and subclinical hypothyroidism

Aim. To evaluate the levels of soluble growth stimulator gene 2 (sST2) protein and N-terminal pro-brain natriuretic peptide (NT-proBNP) in patients with acute coronary syndrome (ACS) depending on the presence of concomitant subclinical hypothyroidism (SH). Materials and methods. 125 patients with ACS aged 36 to 81 years (mean age – 60.98 ± 0.81 years) were included in the study. All the patients were divided into two groups according to the state of thyroid function. Group I consisted of 51 patients (40.8 %) with SH (thyroid-stimulating hormone (TSH) level >4 μIU/mL), mean age – 62.51 ± 1.18 years; Group II – 74 patients (59.2 %) with normal thyroid function (TSH level 0.4–4.0 μIU/mL), mean age – 59.93 ± 1.08 years. The state of SH was diagnosed at a TSH level of >4.0 μIU/mL and a serum free thyroxine (FT4) level within the normal range. Results. In the group of patients with ACS and SH (I), significantly higher mean levels of sST2 and NT-proBNP have been found compared to patients without thyroid dysfunction (II), 46.6 (27.9; 57.7) ng/ml (I) vs. 29.9 (22.0; 38.5) ng/ml (II), p = 0.001 and 173.0 (103.4; 1005.1) ng/l (I) vs. 95.9 (71.8; 178.6) ng/l (II), p = 0.0001, respectively. Among patients with ACS and SH (I), the sST2 level of 35–70 ng/ml was 1.94 times more often, and sST2 >70 ng/ml was 2.28 times more often as compared to those in patients with ACS without thyroid dysfunction (II), 22.74 % (47.06 ± 6.99 % (I) vs. 24.32 ± 4.99 % (II), p = 0.008) and 15.81 % (21.57 ± 5.76 % (I) vs. 9.46 ± 3.40 % (II), p < 0.05), respectively. The study on NT-proBNP levels in ACS patients with SH (I) has revealed a 75.67 % significantly higher proportion of individuals with NT-proBNP levels > 600 ng/L (33.33 ± 6.60 % (I)) as compared to ACS patients with normal thyroid function (II) (8.11 ± 3.17 % (II), p = 0.001). The level of NT-proBNP <125 ng/l has been detected 2.31 times more often in the group of ACS patients with normal thyroid function (II) compared to that in ACS patients with SH (I), by 36.06 % (63.51 ± 5.60 % (II) vs. 27.45 ± 6.25 % (I), p = 0.00002). A significant strong positive correlation has been found in the group of ACS patients with SH (I) (correlation coefficient (r) = 0.775, p < 0.001) in assessing the relationship between the mean levels of sST2 and NT-proBNP. In the group of ACS patients with normal thyroid function (II), a moderate correlation has been found between the mean levels of sST2 and NT-proBNP (r = 0.678, p < 0.001). Conclusions. In the group of ACS patients with moderately reduced thyroid function (SH), significantly higher mean levels of sST2 and NT-proBNP and significantly higher percentage of individuals with sST2 levels ≥ 35 ng/mL, NT-proBNP >600 ng/L have been detected compared to the group of ACS patients with normal thyroid function. These results may indicate a higher risk of development, progression and complications of heart failure due to a higher probability of myocardial fibrosis and subsequent left ventricular remodeling in ACS patients with SH. The significant strong positive correlation has been found between the mean levels of sST2 and NT-proBNP in the group of ACS patients with SH (I) (r = 0.775, p < 0.001). In the group of ACS patients with normal thyroid function (II), the correlation between the mean levels of sST2 and NT-proBNP was less pronounced (r = 0.678, p < 0.001). Combined assessment of these biomarkers may be more informative for the diagnosis and prognosis of heart failure in ACS patients with concomitant thyroid dysfunction than measurements of individual biomarkers. In particular, the simultaneous increase in sST2 and NT-proBNP above reference values allows to identify a very high-risk group for heart failure occurrence and progression in ACS patients.