Thyroid Peroxidase Antibody is Associated with Plasma Homocysteine Levels in Patients with Graves' Disease.

Purpose Homocysteine is associated with cardiovascular, inflammation and autoimmune diseases. Previous studies have shown that thyroid peroxidase antibody is associated with homocysteine levels in hypothyroidism. The relationship between thyroid antibodies and homocysteine in hyperthyroidism remains unclear. In this study, we aimed to investigate the association of thyroid antibodies with homocysteine in patients with Graves' disease. Methods This was a cross-sectional study including 478 Graves' disease patients who were consecutively admitted and underwent radioiodine therapy. Homocysteine, thyroid hormones, thyroid antibodies, glucose and lipids were measured. Results Patients with homocysteine levels above the median were older and had unfavorable metabolic parameters compared to patients with homocysteine levels belowthe median. Thyroglobulin antibody or thyroid peroxidase antibody was associated with homocysteine levels (beta = 0.56, 95 %CI 0.031.08, p = 0.04; beta = 0.75, 95 %CI 0.23-1.27, p =0.005). The relationship between thyroid peroxidase antibody and homocysteine remained significant when additionally adjusting for free triiodothyronine (beta =0.76, 95 %CI 0.24-1.28, p=0.004). The presence of a homocysteine level above the median increased sign ificantlywith increasing thyroid peroxidase antibody quartiles in the logistic regression (OR = 1.74, 95 %CI 1.27-2.39, P fortrend =0.001). Homocysteine levels increased significantly with increasing thyroid peroxidase antibody quartiles (p = 0.005). Thyroid peroxidase antibody had no significant effect on other traditional cardiovascular risk factors. Conclusions Thyroid peroxidase antibody is independently and positively associated with homocysteine levels in patients with Graves' disease. Thyroid peroxidase antibody may be associated with the cardiovascular risk of patients with Graves' disease through its effect on homocysteine.