source: Endocrine Society

year: 2016

authors: Helena Greenfield, Celestino Neves, Sofia Castro Oliveira, João Sérgio Neves, Camila Dias, Oksana Sokhatska, Davide Carvalho, Luís Delgado, José Luís Medina

Introduction:
The cardiovascular system function is modulated by thyroid hormone levels. The antibodies involved in Graves’ disease are central to the pathophysiological consequences of the disease but the impact of their evolution over time is still an area of interest.

Aim:
To evaluate the relationship between thyroid function, autoimmunity, insulin resistance and cardiovascular risk factors in patients with Graves’ disease. 

Methods:
We analyzed thyroid function, TRABs, anti-TPO and anti-thyroglobulin antibodies (anti-Tg), BMI, insulin resistance markers comprising the HOMA-IR, QUICKI, HISI (Hepatic Insulin Sensitivity Index), WBISI (Whole-Body Insulin Sensitivity Index), IGI (Insulinogenic Index) and the levels of total cholesterol (TC), HDL, LDL-cholesterol, triglycerides, ApoB, ApoA1, Lp(a), homocysteine, CRP (C-reactive protein), folic acid and vitamin B12 levels in 122 patients (92.6% women) with Graves’ disease: 59 euthyroid patients, 22 hyperthyroid patients and 28 patients with subclinical hyperthyroidism (TSH <0.35 µUI/ml and normal levels of FT4 and FT3). These groups were followed between 2012 and 2015. Mann-Whitney test and Spearman correlations were used for statistical analysis. A two-tailed value of p <0.05 was considered statistically significant. The results are expressed as means ±SD. 

Results:
CRP levels were significantly higher in the hyperthyroid group when compared with the euthyroid group (0.62±0.42 vs 0.24±0.23 mg/L, p=0.042). TRABs were statistically higher in the hyperthyroid group when compared with the subclinical hyperthyroid group (9.65±11.82 vs 7.45±9.97 IU/mL, p<0.001) and with the euthyroid group (9.65±11.82 vs 2.66±5.82 IU/mL, p<0.001). Anti-Tg levels decreased on follow-up in the hyperthyroid group (117.2±159.75 vs 43.31±90.8 IU/mL, p=0.044). There was a progressive lowering of the anti-TPO (562.07±537.63 vs 260.61±364.27 IU/mL, p<0.001) and TRABs (5.12±8.50 vs 1.82±3.48 IU/mL, p<0.001) in all groups from the first measurement up until the current values. In the hyperthyroid group there was a correlation between FT3 and total cholesterol (r=-0.751; p=0.001), LDL (r=-0.781; p=0.001), vitamin B12 (r=0.718; p=0.013) and TRABs (r=0.838; p=0.001) and between FT4 and folic acid (r=0.61; p=0.027) and TRABs (r=0.629; p=0.038). In the total group, FT3 levels were positively correlated with QUICKI (r=0.490, p<0.001), HISI (r=0.478, p<0.001) and WBISI (r=0.401, p<0.001), and were negatively correlated with HOMA-IR (r=-0.478, p<0.001) and IGI (r=-0.246, p=0.028). 

Conclusion:
In patients with Graves’ disease, the evolution of antibodies levels appears to be associated with changes in thyroid function and in cardiovascular risk factor, highlighting the potential relevance of the interactions between autoimmunity and thyroid function to long-term outcomes of patients with Graves’ disease.

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