Elevated liver enzymes generally indicate some abnormality with the organ. Your liver enzymes rise when damage to liver cells releases them into the bloodstream. You often experience itching skin if you have severe jaundice, another indicator of liver disease. Jaundice occurs when levels of bilirubin, produced from the breakdown of red blood cells, rise, either because of a blockage in your bile ducts or from liver damage. Symptoms of liver disease can occur if you have taken medications that can harm the liver, or in acute illnesses such as hepatitis A or chronic liver diseases like cirrhosis.
Types of Liver Enzymes
A routine liver function panel includes four tests: aspartate aminotransferase (AST), or SGOT; alanine aminotransferase (ALT), or SGPT; alkaline phosphatase (ALP), or AP; and gamma-glutamyl transferase (GGT). While ALT comes mainly from the liver, AST is also found in the heart, kidneys and muscles, so an elevation of AST is less diagnostic for liver disease than an elevation of ALT. Elevations of GGT and ALP often occur when damage affects the bile ducts connected to the liver. While GGT occurs mostly in the liver, ALP is also found in bones, intestines and kidneys. ALT readings normally range from 0 to 45 IU/L while AST falls between 0 and 40 IU/L. The normal ALP range is from 35 to 115 IU/L, and GGT from 3 to 60 IU/L.
Bilirubin and Itching
Bilirubin is a byproduct of the breakdown of old red blood cells. After around 120 days, your body removes old red blood cells from circulation and breaks them down. Bilirubin is processed by liver cells to produce bile, which is removed via the bile ducts for disposal through your urine or stool. Cell damage in your liver, or bile duct damage, can cause bilirubin to accumulate and leak into the skin, causing jaundice. Accumulated bilirubin in the skin also causes itching. Bile duct obstruction can cause severe itching.
Elevations of Labs and Diagnosis
The types and ratios of liver enzyme elevations can often indicate the type of disease process present in your system. In alcohol abuse, while elevations occur in both AST and ALT, the ratio of AST to ALT is greater, usually 2:1. In nonalcoholic steatohepatitis (NASH), the AST to ALT ratio is usually less than 1:1. In acute liver injury caused by drugs or viruses, AST and ALT readings may rise to the 10,000s. In bile duct disease such as cholangitis, GGT and ALP may elevate to 10 times their normal concentrations. Bilirubin may rise above its normal level of 2.5 mg/dL.
Disorders Associated With Itching
Any disorder that causes liver enzyme elevations and high bilirubin levels can cause itching. As many as 20 percent of people with hepatitis C experience pruritus, or intense itching, according to the HCV Advocate. Itching increases in people with more advanced disease. Diseases that block the bile ducts, such as primary sclerosing cholangitis, also often cause intense itching. Blockage of the bile ducts from gallstones can also cause your bilirubin levels to rise, resulting in pruritus.
- Liver Disease.com; Liver Enzymes; Melissa Palmer, M.D.
- Jackson/ Siegelbaum Gatroenterology; Primary Sclerosing Cholangitis; Frank Jackson, M.D.
- Q notes for Adult Medicine; Clinical Approach to Abnormal Liver Enzyme Tests; 2005
- Hepatitis C Support Project; Pruritis; C. Mazoff, Ph.D.; Febraury 2009
- MedlinePlus; Biliburbin-Blood; February 2009
- NetDoctor UK; Jaundice; November 2010