The Role of Serum C-Reactive Protein Measured by High-Sensitive Method in Thyroid Disease

The aim of this study was the evaluation of serum C-reactive protein (CRP) concentration as a marker of the inflammatory state in many different thyroid diseases and its dependence on the stage and duration of disease. We conducted a retrospective analysis of 444 randomly selected patients with different kinds of thyroid disease (106 men and 338 women, ranging 18–72 years of age; mean 56.2 ± 5.0 years; median 52 years). Group 1 (G1) comprised 250 patients with hyperthyroidism. Group 2 (G2) consisted of 72 euthyroid patients. Group 3 (G3) consisted of 122 patients with hypothyroidism. Free T4, free T3, and thyrotropin (TSH) levels were measured using the electrochemiluminescent method. Human serum thyroglobulin autoantibodies (Tg-Abs), thyroperoxidase autoantibodies (TPO-Abs), and autoantibodies against the thyrotropin receptor (TSHR-Abs) levels were measured by radioimmunoassay. The high-sensitive CRP (Hs-CRP) level (reference range <3 mg/L) was determined with a highly sensitive latex-based immunoassay. The mean value of Hs-CRP in G1 was 3.6 ± 2.8 mg/L, in G2 2.5 ± 1.5 mg/L and in G3 5.9 ± 5.8 mg/L. Hs-CRP (in mg/L) medians, interquartile and the total ranges in G1 were 3.0 (2.0 [0.1–21.0] 4.0); in G2: 2.3 [1.8 (0.2–9.2) 3.2]; and in G3: 4.3 [2.2 (0.3–31.5) 7.8]. We found statistically significant differences (Kruskal–Wallis test) in serum Hs-CRP values between G1 and G2 (P = 0.007), G1 and G3 (P = 0.001), G2 and G3 (P < 0.001). In G1, statistically significant correlation was confirmed between Hs-CRP and Tg-Abs (r = −0.22, P = 0.0016), CRP and TPO-Abs (r = −0.26, P < 0.001), and also between Hs-CRP and TSHR-Abs (r = −0.18, P = 0.02). In the remaining cases, differences between Hs-CRP and TSH levels (r = −0.09, P = 0.16) were not statistically significant. In G2, no statistically significant correlation was observed: Hs-CRP and Tg-Abs (r = −0.18, P = 0.13), Hs-CRP and TPO-Abs (r = −0.17, P = 0.15), Hs-CRP and TSH (r = 0.01, P = 0.91), Hs-CRP and TSHR-Abs (r = −0.19, P = 0.17). In G3, a statistically significant correlation was confirmed between Hs-CRP and Tg-Abs (r = 0.22, P = 0.012), Hs-CRP and TSH (r = −0.28, P = 0.001). No statistically significant correlation was observed between Hs-CRP and TPO-Abs (r = 0.20, P = 0.06) and between Hs-CRP and TSHR-Abs (r = −0.23, P = 0.11). Hs-CRP is increased in various types of hypothyroidism. This is particularly relevant in postpartum thyroiditis and in patients after radioiodine treatment. The impact of this situation on human health requires further research, however, one might assume that some types of thyroid disease may lead to systemic inflammatory reactions that are reflected in elevated CRP levels.