Low normal thyroid function attenuates serum alanine aminotransferase elevations in the context of metabolic syndrome and insulin resistance in white people

Objectives: Thyroid hormones play a key role in hepatic lipid metabolism. Although hypothyroidismis associated with increased prevalence of non-alcoholic fatty liver disease (NAFLD), the relationship of NAFLD with low normal thyroid function is unclear. We tested the association of serum alanine transferase (ALT), as a surrogate of NAFLD, with variations in thyroid function within the normal range. Design and methods: Thyroid stimulating hormone (TSH), free T-4, ALT, insulin resistance (homeostasis model assessment (HOMA-IR)) and adiponectin were measured in 82 non-diabetic white subjects with TSH and free thyroxine (free T-4) levels within the reference range. Nineteen participants were classified with metabolic syndrome (MetS). Results: ALT was higher in MetS subjects (p <0.05), coinciding increased HOMA-IR (p <0.001). TSH and free T-4 levels were not different in subjects with and without MetS. In all subjects combined, ALT was correlated positively with HOMA-IR and inversely with adiponectin (both p