Fatty Liver Disease: This is the most common cause of isolated elevated GGT (Gamma-Glutamyl Transferase) in adults. Fatty liver disease, particularly non-alcoholic fatty liver disease (NAFLD), is increasingly prevalent and can be associated with metabolic syndrome, obesity, and insulin resistance. An isolated GGT elevation of 50 in a 48-year-old woman could be an early indicator of this condition, especially if she has risk factors such as obesity or a family history of diabetes.

Alcohol Use: Although the patient's GGT level is not extremely high, chronic alcohol consumption can cause elevations in GGT. Even moderate alcohol use can lead to increased GGT levels, especially in susceptible individuals.
Medication-Induced: Certain medications, including statins, anticonvulsants, and some antibiotics, can cause elevations in liver enzymes, including GGT.
Hypothyroidism: Some studies suggest a link between hypothyroidism and elevated liver enzymes, including GGT, possibly due to decreased hepatic blood flow or other metabolic effects.

Hepatitis C: Although less common, hepatitis C infection can cause chronic liver inflammation and elevation of liver enzymes, including GGT. Given the potential for severe consequences if left untreated, it's crucial not to miss this diagnosis.
Primary Biliary Cholangitis (PBC): An autoimmune disease that affects the bile ducts, leading to cholestasis and potential liver damage. Early detection is critical for managing the disease and preventing progression to cirrhosis.
Wilson's Disease: A rare genetic disorder that leads to copper accumulation in the liver, causing liver damage. Although rare, it's essential to consider in young patients with unexplained liver enzyme elevations.

Alpha-1 Antitrypsin Deficiency: A genetic disorder that can cause liver disease and elevation of liver enzymes, including GGT. It's rare but should be considered in patients with a family history of liver disease or lung disease.
Cystic Fibrosis: Although primarily known for its respiratory manifestations, cystic fibrosis can also affect the liver, leading to focal biliary cirrhosis and elevated liver enzymes.
Budd-Chiari Syndrome: A rare condition caused by thrombosis of the hepatic veins, leading to liver congestion and enzyme elevations. It's essential to consider in patients with risk factors for thrombosis.