5′-Nucleotidase

5′-Nucleotidase (5′-NT) is an enzyme that catalyzes the hydrolysis of nucleotides (e.g., AMP → adenosine + phosphate). In clinical practice, it is mainly used as a marker of hepatobiliary disease.

1. Marker of Cholestasis and Hepatobiliary Disease

5′-NT is primarily present in:

• Liver (especially bile canalicular membranes)
• Bile ducts
• Intestinal mucosa (minor contribution)
• Elevated serum levels are seen in:
• Obstructive jaundice
• Intrahepatic cholestasis
• Drug-induced cholestasis
• Hepatic tumors

👉 Therefore, increased 5′-NT suggests biliary obstruction or liver cell damage involving bile flow.

2. Differentiation from Bone Disease (vs. ALP)

Both Alkaline Phosphatase (ALP) and 5′-NT increase in cholestasis. However:

Condition ALP 5′-NT
Liver disease ↑ ↑
Bone disease ↑ Normal

🔎 Clinical Importance:

If ALP is elevated and 5′-NT is also elevated → likely hepatic origin

If ALP is elevated but 5′-NT is normal → likely bone disease (e.g., Paget’s disease, rickets)

Thus, 5′-NT helps confirm that raised ALP is due to liver pathology, not bone disorders.

3. Conditions Associated with Increased 5′-NT

Extrahepatic biliary obstruction (e.g., gallstones)

Intrahepatic cholestasis

Cirrhosis

Hepatitis

Metastatic liver disease

Levels often parallel ALP in hepatobiliary conditions.

4. Conditions Where It Is NOT Elevated

Bone diseases

Pregnancy-related ALP elevation (placental ALP)

Growing children (bone growth)

This specificity makes 5′-NT particularly useful in ambiguous ALP elevations.