What are the potential sources of abnormal liver function test results, including elevated SGOT (Serum Glutamic-Oxaloacetic Transaminase), PT (Prothrombin Time), and ALP (Alkaline Phosphatase), in a patient with scalp psoriasis or seborrheic dermatitis?

Sources of Elevated SGOT/AST, PT, and ALP

Understanding the Enzyme Sources

ALT (SGOT) is the most liver-specific enzyme, while AST, PT, and ALP have multiple extrahepatic sources that must be considered when evaluating abnormal liver function tests. 1

ALT/SGOT Sources and Specificity

• ALT is highly specific for liver injury because it is primarily concentrated in liver tissue with minimal presence in other organs 1, 2
• ALT has low concentrations in skeletal muscle and kidney, making elevations strongly indicative of hepatocellular damage 1
• Normal ALT ranges are sex-specific: 29-33 IU/L for men and 19-25 IU/L for women 1, 2

AST Sources (Less Liver-Specific)

• AST is significantly less liver-specific than ALT because it is present in multiple tissues 2
• AST is found in cardiac muscle, skeletal muscle, kidneys, brain, and red blood cells 1, 2
• Extrahepatic causes of AST elevation include:
  • Cardiac injury (myocardial infarction, myocarditis) 1
  • Skeletal muscle disorders (rhabdomyolysis, muscular dystrophy, intensive exercise) 1, 2
  • Hemolysis (red blood cell destruction) 2
  • Renal disorders 1

PT (Prothrombin Time) Sources

• PT reflects hepatic synthetic function rather than hepatocellular injury 1
• PT is prolonged when liver synthetic capacity is impaired, indicating advanced liver disease 1
• Non-hepatic causes of prolonged PT include:
  • Vitamin K deficiency 1
  • Warfarin or anticoagulant therapy 1
  • Disseminated intravascular coagulation 1
  • Congenital coagulation factor deficiencies 1

ALP (Alkaline Phosphatase) Sources

• ALP is primarily elevated in cholestatic disorders but has significant extrahepatic sources 1
• Hepatic sources: Biliary obstruction, cholestasis, infiltrative liver disease 1
• Extrahepatic sources of ALP elevation include:
  • Bone diseases (Paget's disease, bone metastases, fractures, osteomalacia) 1
  • Pregnancy (placental ALP) 1
  • Malignancy with bone involvement 1
  • Chronic kidney disease 1

Clinical Context: Psoriasis and Seborrheic Dermatitis

Medication-Induced Liver Injury

In patients with scalp psoriasis or seborrheic dermatitis, methotrexate is the most common cause of abnormal liver function tests. 1, 3

• Methotrexate causes hepatotoxicity, fibrosis, and cirrhosis with prolonged use 3
• Acute liver enzyme elevations (ALT/AST) are frequently seen and usually transient 3
• Persistent abnormalities in liver function tests may precede fibrosis or cirrhosis in the rheumatoid arthritis population 3
• 12 of 44 patients (27%) treated with oral methotrexate dropped out due to abnormal liver function tests in one study 1

Systemic Therapy Considerations

• Acitretin causes transaminase elevations in up to 16% of patients and triglyceride elevations in 25-50% 1
• Cyclosporine can cause hepatotoxicity, particularly when combined with other hepatotoxic agents 1
• Alcohol consumption significantly increases hepatotoxicity risk with methotrexate and acitretin 1, 3

Metabolic Syndrome and NAFLD

• Patients with psoriasis have increased prevalence of metabolic syndrome components (obesity, diabetes, hypertension, dyslipidemia) 1
• Non-alcoholic fatty liver disease (NAFLD) is common in this population and presents with AST:ALT ratio <1 2
• Metabolic syndrome increases risk for steatohepatitis, which can elevate liver enzymes independently of psoriasis treatment 1

Diagnostic Algorithm for Abnormal LFTs

Initial Evaluation

• Obtain complete liver panel: ALT, AST, ALP, GGT, total and direct bilirubin, albumin, PT/INR 1, 2
• Check creatine kinase (CK) to exclude muscle injury as source of transaminase elevation 1, 2
• Review all medications against LiverTox® database for hepatotoxic potential 2
• Assess alcohol consumption history (>40g/day for women, >50-60g/day for men) 2

Pattern Recognition

• Hepatocellular pattern: ALT/AST elevation predominates, suggests hepatocyte injury 1
• Cholestatic pattern: ALP elevation predominates, suggests biliary obstruction or cholestasis 1
• Mixed pattern: Both hepatocellular and cholestatic enzymes elevated 1

Common Pitfalls

• Do not assume isolated ALP elevation is hepatic without checking GGT or bone-specific markers 1
• Intensive exercise can cause acute AST/ALT elevations that may be mistaken for liver injury 2
• AST/ALT ratio >2 is highly suggestive of alcoholic liver disease and should prompt detailed alcohol history 2
• Women have lower normal ALT ranges than men, making elevations more significant in female patients 2