Subclinical Hypothyroidism and the Effect of Autoimmunity on the Echocardiography Indices of Left Ventricular Function, Lipid Profile, and Inflammatory Markers

Background: Subclinical hypothyroidism (Sch) is the most frequent thyroid disease. The relationship between overt hypothyroidism and cardiovascular diseases has been well documented, but conflicting data have remained regarding Sch.

Objectives: The present study aimed to assess the effect of Sch on increasing the risk of cardiovascular involvement considering the autoimmune subset.

Patients and Methods: This case-control study was conducted on thirty patients with Sch and 30 healthy controls. Serum levels of thyroperoxidase antibody (TPOab), lipids, hsCRP, homocysteine, and ferritin were measured. Besides, conventional echocardiographic study and tissue Doppler imaging (including strain rate indices) was done to evaluate Left Ventricular (LV) systolic function.

Results: The results showed a significant difference between the Sch patients and the controls regarding the serum level of triglyceride (117.43 ± 63.51 mg/dL vs. 86.86 ± 41.57, P = 0.031), echocardiographic parameters (longitudinal systolic strain rate [SRs: -1.006 ± 0.4 vs. -1.26 ± 0.16, P = 0.002; SRl: -1.43 ± 0.27 vs. -1.68 ± 0.29, P = 0.001]), and Sm of septal mitral annulus (6.90 ± 0.6 vs. 7.43 ± 0.8, P = 0.006)]. However, no significant difference was observed between the two groups regarding the serum levels of the inflammatory markers. Moreover, a significant correlation was found between TSH and Sm (r = -0.36, P = 0.005) and longitudinal systolic strain rate (SRs: r = 0.42, P < 0.001; SRl: r = 0.40, P = 0.001). Systolic strain rate was significantly lower in the TPOab positive patients (-0.99 ± 0.18 vs. -1.15 ± 0.25, P = 0.047).

Conclusions: The clear association between Sch and subclinical LV systolic dysfunction which was more evident in the subgroup of patients with circulating anti-thyroid antibodies would remind a greater emphasis for considering the subgroup of TPOab positive patients for directing toward hormone replacement.