Metabolic dysfunction-associated steatotic liver disease, or metabolically-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease, has become the leading chronic liver disease worldwide in the last decade. The spectrum of MASLD ranges from simple hepatic steatosis to metabolic-associated steatohepatitis (MASH), advanced liver fibrosis, liver cirrhosis, and hepatocellular carcinoma. Hepatic inflammation and progressive fibrosis are considered to be the most important driving forces for the progression of MASLD/MASH. Therefore, patients with MASH are a key target group for the development of new therapeutic agents. Although many clinical trials have been conducted in patients with MASLD/MASH over the past two decades, until recently there was no licensed drug for the treatment of this very common metabolic liver disease. Preclinical experimental studies and results from human studies have confirmed the importance of thyroid hormone receptor-β (TGR-β) in the development of hepatic steatosis and stimulated interest in the development of TGR-β agonists as potential treatments for MASLD. The effects of TGR-β agonists, mainly resmetirom, on hepatic and cardiometabolic risk factors have been tested in randomized placebo-controlled trials (RCTs) in patients with MASLD/MASH. As a result of the positive data obtained in the phase III RCT (MAESTRO-NASH), the USA FDA agency on March 14, 2024 accelerated approval of the first TGR-β agonist resmetirom as a drug for the treatment of steatohepatitis associated with metabolic dysfunction. Thus, resmetirom has become the first officially approved drug to be recommended in combination with diet and exercise for use in adults with non-cirrhotic MASH with moderate or advanced liver fibrosis (stages F2-F3 fibrosis).