Low-Normal Thyroid Function Is Associated With Advanced Fibrosis Among Adults in the United States

The pathogenetic pathways leading to increasing prevalence of advanced fibrosis in the setting of nonalcoholic fatty liver disease (NAFLD) and resulting in higher rates of liver-related and cardiovascular morbidity and mortality in the United States are multifactorial.¹ The negative health impact of "low-normal" thyroid function, which is defined as a higher level of thyroid-stimulating hormone (TSH) within the euthyroid reference range, may be comparable with overt and subclinical hypothyroidism.^2-4 We reported a strong association between biopsy-proven advanced fibrosis in NAFLD with increasing TSH levels in a dose-dependent manner even within the euthyroid reference range.⁵ To generalize our findings across all ethnicities, we examined the association of both low-normal thyroid function and subclinical hypothyroidism with advanced fibrosis in the US general population.