Signs and symptoms
People with NAFLD often have no noticeable symptoms, and NAFLD is often only detected during routine blood tests or unrelated abdominal imaging or liver biopsy. In some cases, NAFLD can cause symptoms related to liver dysfunction such as fatigue, malaise, and dull right-upper-quadrant abdominal discomfort. Mild yellow discoloration of the skin may occur, although this is rare. NASH can severely impair liver function, leading to cirrhosis, liver failure, and liver cancer. Comorbidities
NAFLD is strongly associated with or caused by type 2 diabetes, insulin resistance, and metabolic syndrome (defined as at least three of the five following medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein). It is also associated with hormonal disorders (panhypopituitarism, hypothyroidism, hypogonadism, polycystic ovary syndrome), persistently elevated transaminases, increasing age and hypoxia caused by obstructive sleep apnea, with some of these conditions predicting disease progression.The majority of normal-weight people affected by NAFLD ("lean NAFLD") have impaired insulin sensitivity, are sedentary, and have increased cardiovascular disease risk and increased liver lipid levels. These are the consequences of a decreased capacity for storing fat and reduced mitochondrial function in adipose tissue and increased hepatic de novo lipogenesis. A recent systematic review has reported an increased risk of severe COVID-19 infection in NAFLD patients; however, no difference in mortality was observed between NAFLD and non-NAFLD patients. Risk factors
Genetics
Two-thirds of families with a history of diabetes type 2 report more than one family member having NAFLD.
Low thyroid activity is more prevalent in people with NASH, which would be detected by determining the thyroid-stimulating hormone. Some biomarker-based blood tests have been developed and may be useful for diagnosis.Although blood tests cannot diagnose NAFLD, circulating serum biomarkers of liver fibrosis can give moderate estimates in the diagnosis of liver fibrosis and cirrhosis. The ratio of the transaminase liver enzyme aspartate aminotransferase (AST) to platelets in the blood, known as the AST/platelet ratio index (APRI score), and Fibrotest are recommended as the preferred noninvasive tests for cirrhosis by the Asian-Pacific Association for Study of the Liver (APASL). Several other scores such as FIB-4 score and NAFLD fibrosis score can also reflect the burden of the fibrosis in the liver, and previous studies have confirmed that these score can predict future development of mortality and liver cancer. Imaging
A liver ultrasound scan or magnetic resonance imaging (MRI) can diagnose steatosis, but not fibrosis and confirmation of early cirrhosis detection by ultrasound by other diagnostic methods is recommended. The European Association for the Study of the Liver (EASL) recommends screening for steatosis whenever NAFLD is suspected as this is a strong predictor of the disease evolution and predicts future type 2 diabetes, cardiovascular events, and hypertension.