We report a rare case highlighting the progression of liver disease in a male patient with idiopathic childhood-onset growth hormone (GH) deficiency. The patient was diagnosed with hypopituitarism at six years old and was treated with thyroxine therapy and GH for his short stature, with testosterone added at the age of 15. GH therapy was discontinued when the patient was 18 years old, but thyroid and testosterone treatments continued. The patient had been taking medication for hyperlipidemia until the age of 30 and was noted to have impaired glucose tolerance at the age of 40, but HbA1c levels remained normal. At the age of 47, esophageal varices were incidentally discovered via endoscopy, revealing liver cirrhosis. Laboratory tests showed liver dysfunction and abnormal lipid levels, and hepatitis viral markers were absent. The patient had no history of drinking alcohol or smoking, and no family history of diabetes. Ultimately, this case demonstrates that metabolic dysfunction-associated steatotic liver disease (MASLD/metabolic dysfunction-associated steatohepatitis (MASH)) is under-recognized in GH deficiency cases and can progress to liver cirrhosis. Therefore, careful evaluation of MASLD/MASH in childhood-onset GH deficiency is necessary, and GH replacement therapy should continue into adulthood, if possible.