Evaluation of thyroid function and thyroid autoimmune disease in patients with non-alcoholic fatty liver disease

Introduction
Evaluation of thyroid function and thyroid autoimmunity in patients with non-alcoholic fatty liver disease (NAFLD).

Material and methods
A case control study. Fifty patients with NAFLD and 50 control subjects matched by gender and age were recruited. Serum thyroid stimulating hormone (TSH) and free thyroxine (FT4) were measured to assess thyroid function. Thyroid autoimmune disease was evaluated by measuring thyroid peroxidase antibody (TPOAb) and anti-thyroglobulin antibodies (TgAb). The FIB-4 score and the APRI score were calculated to assess the degree of fibrosis. The association between thyroid parameters and NAFLD was explored.

Results
About one quarter of patients with NAFLD had hypothyroidism compared to 10% of the control group whilst 6% of NAFLD patients had hyperthyroidism compared to 2% of the controls. NAFLD cases showed substantially higher TSH and lower FT4 compared to controls; meanwhile, levels of fibrosis indices (FIB-4 and APRI score) were significantly higher among hypothyroid patients in both cases and controls. TSH had a positive strong correlation with FIB-4 and APRI score, whereas FT4 had a negative significant correlation with both fibrosis indicators, and this clinical relationship was similar in NAFLD cases and controls.

Conclusions
Hypothyroidism is more prevalent among patients with NAFLD compared to controls and high levels of TSH with low FT4 might be a risk factor for NAFLD and may impact the development of liver fibrosis. The role of thyroid autoimmunity in NAFLD needs further assessment. NAFLD patients should be monitored by yearly TSH and FT4 testing.