Relationship between hypothyroidism and non-alcoholic fatty liver disease in the Spanish population.

Background: Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disease in developed countries and is considered the hepatic component of metabolic syndrome (MetS). Recently hypothyroidism has been associated with NAFLD but has never been studied in Spain.

Objectives: To analyze the relationship between hypothyroidism (clinical and subclinical) and NAFLD. To determine the association between MetS with NAFLD and hypothyroidism.

Methods: Cross-sectional, retrospective, population study in subjects ≥45 years from primary care centres in Catalonia included in the SIDIAP database. The data was collected between 2009 and 2013.

Variables: socio-demographic data, comorbidities, toxic habits, physical examination, analytical tests and diagnosis of MetS. Descriptive analysis and application of statistical tests for the comparison of variables.

Results: Sample of 10,116 individuals with a mean age of 61(10) and a predominance of females (63.6%). The prevalence of hypothyroidism was 9.1%, with no significant differences according to the presence of NAFLD (p=.631). Hypothyroidism was associated with higher triglyceride levels and a greater prevalence of obesity (p=.003). Greater alteration of AST was detected in individuals with elevated TSH (p=.012) and decreased levels of T4L (p=.037). Alterations in thyroid hormone levels were not associated with a higher prevalence of NAFLD (TSH p=.072 and T4L p=.447). Hypothyroidism was not considered a risk factor for the development of NAFLD (OR .75; 95% CI: .39-1.44; p=.38).

Conclusions: No association was found between hypothyroidism and NAFLD. Prospective studies are needed to clarify a possible relationship between these two diseases.