Levels of Antithyroid Antiperoxidase and Antithyroglobulin Antibodies in Patients with Graves Hyperthyroidism – Predictors of Initial and Sustained Remission and Consecutive Hypothyroidism

Abstract

BACKGROUND: Initial and sustained remission is the principal objective in patients with Graves hyperthyroidism (GH) treated with antithyroid drugs (ATD). AIMS: Our study aimed to investigate the predictive value of antithyroid antiperoxidase (aTPO) and antithyroglobulin (aTg) levels on initial and sustained remission or consecutive hypothyroidism in subjects with GH treated with ATD. METHODS: Randomized, prospective, and longitudinal study during period 2013–2018 was performed. Eighty GH patients (thyrotropin [TSH] <0.01 mIU/L, free thyroxine [FT4] >30 pmol/L, triiodothyronine [FT3] >8 pmol/L), 59 females (73.75%), and 21 males (26.25%), aged 51 ± 12 years were included in the study. Subjects were divided into four subgroups (each with 20 patients) according to aTPO and aTg levels: Group I – no antibodies; Group II – (<500 IU/mL), Group III – (500–1000 IU/mL), and Group IV – (>1000 IU/mL). All subjects underwent 24 months of propylthiouracil treatment with follow-up of 24 months after remission (TSH >0.4 mIU/L, FT4 11–25 pmol/L, FT3 2.8–6.5 pmol/L). Blood samples were analyzed every 4 months. RESULTS: In Group I, 11 (55%) of the patients attained remission; during follow-up, 5 (45%) of them had disease relapse. In Group II, 12 (60%) attained remission and 5 (42%) had relapse. In Group III, 15 (75%) attained remission, 2 (13%) had disease relapse, and 4 (26%) developed hypothyroidism. In Group IV, 18 (90%) attained remission, 1 (5%) had disease relapse, and 9 (50%) developed hypothyroidism. Patients with values below 500 IU/mL attained remission in 60%, similar as the group without antibodies in 55% (p < 0.3). Patients in Group III and IV had significantly higher remission rates compared to Group I and II (p < 0.001). Baseline values of aTPO and aTg >1000 IU/mL were significant predictors of consecutive hypothyroidism (p < 0.05). CONCLUSION: Baseline aTPO and aTg values above 500 IU/mL were significantly prognostic for attaining and  sustaining  remission  in  GH  and  values  above  1000  IU/mL  were  significant  predictors  of  consecutive hypothyroidism.