Incidences of hypothyroidism and autoimmune thyroiditis are increased in patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disease, with about one in four people being affected in most areas of the world. Due to its strong association with metabolic syndrome, NAFLD is associated with high morbidity and mortality. Recent data have suggested a pathophysiological association between NAFLD and thyroid disease, but most studies are explorative and results remained conflicting. Here, we aimed at evaluating a potential association between NAFLD and hypothyroidism as well as autoimmune thyroiditis primary care patients in Germany.Incidence rates of hypothyroidism and autoimmune thyroiditis were compared between a cohort of n = 40,583 patients with NAFLD and a cohort of equal size without NAFLD that was matched by sex, age, index year, obesity and diabetes within 10 years from the index date.Within the 10 years observation period, incidence of hypothyroidism was significantly higher among patients with NAFLD compared to patients without NAFLD [hazard ratio: 1.53 (95% confidence interval, 1.43-1.64), P < 0.001]. Importantly, regression analysis revealed that the association was significant in both men and women patients as well as in patients from all age groups. Moreover, NAFLD patients showed a significantly higher incidence rate of autoimmune thyroiditis compared to patients without NAFLD [hazard ratio: 1.55 (95% confidence interval, 1.34-1.79), P < 0.001]. This association was most pronounced in patients >70 years.Our study provides strong evidence for a significant association between NAFLD and hypothyroidism as well as autoimmune thyroiditis in a large population-based cohort in Germany. This finding should trigger a particular awareness of thyroid diseases in this increasingly important patient group.