Amylase is a digestive enzyme that breaks down complex carbohydrates into simpler sugars. Found throughout the body, it aids in the initial stages of food digestion. This article focuses on serum amylase, which refers to its levels measured in the bloodstream.
What Amylase Is and Where It Comes From
Amylase is an enzyme primarily produced by two organs: the pancreas and the salivary glands. The pancreas releases pancreatic amylase into the small intestine, where it continues the digestion of starches begun in the mouth. Salivary amylase, secreted in saliva, starts the breakdown of carbohydrates as soon as food enters the mouth.
The specific type of amylase, whether pancreatic or salivary, can sometimes be identified through laboratory tests, though a standard serum amylase test measures the total amount from both sources. Pancreatic amylase is particularly important for nutrient absorption in the gut. Salivary amylase, also known as ptyalin, begins the hydrolytic process of starch into maltose and dextrin.
Why Serum Amylase Levels Are Tested
Doctors often order a serum amylase test to investigate symptoms that might suggest a problem with the pancreas. These symptoms can include severe abdominal pain, nausea, vomiting, or a loss of appetite. The test is commonly used to help diagnose or monitor conditions affecting the pancreas, such as inflammation.
The test helps in the assessment of acute pancreatitis, a sudden inflammation of the pancreas, by indicating elevated enzyme release. It may also be used to monitor the course of known pancreatic diseases or to evaluate the effectiveness of treatment. Sometimes, it is part of a broader panel of blood tests when a patient presents with generalized abdominal discomfort.
Understanding Amylase Test Results
Normal serum amylase levels typically range from about 30 to 110 units per liter (U/L), though this range can vary slightly between laboratories. Deviations from this range can indicate underlying health conditions. Interpreting these results requires careful consideration of a patient’s symptoms, medical history, and other diagnostic findings.
Elevated amylase levels often suggest acute pancreatitis, where the inflamed pancreas releases a surge of the enzyme into the bloodstream. Levels can increase within hours of the onset of pancreatitis and may remain high for several days. A rise of three or more times the upper limit of the normal range is highly suggestive of this condition. Chronic pancreatitis, especially during acute flare-ups, can also lead to elevated serum amylase levels.
Problems with the salivary glands can also cause high amylase, as these glands produce a significant amount of the enzyme. Conditions such as mumps, which causes inflammation of the parotid glands, or blockages in the salivary ducts can lead to increased serum amylase. Certain abdominal emergencies, like a perforated ulcer or a bowel obstruction, can sometimes result in elevated amylase due to damage or inflammation in nearby tissues.
Kidney failure can also cause elevated amylase levels because the kidneys are responsible for clearing amylase from the blood. Certain cancers, particularly those affecting the pancreas or ovaries, may also produce or release amylase, resulting in higher-than-normal levels. Some medications, including certain diuretics and opioids, are known to influence amylase levels and can cause an increase. Therefore, a complete medication history is important when evaluating test results.
Conversely, lower-than-normal serum amylase levels are less common but can also indicate specific health issues. Severely damaged pancreatic tissue, as seen in extensive chronic pancreatitis or advanced pancreatic cancer, might lead to reduced amylase production. Conditions like cystic fibrosis, which affects exocrine gland function, can also result in lower amylase levels over time due to progressive pancreatic damage. Pre-eclampsia, a pregnancy complication, has also been associated with decreased serum amylase activity.
Comparing Amylase and Lipase Tests
While both serum amylase and serum lipase tests are used to evaluate pancreatic health, they offer distinct advantages. Lipase is another enzyme produced by the pancreas, primarily responsible for breaking down fats. When the pancreas is inflamed, lipase is released into the bloodstream, similar to amylase.
Lipase is often considered more specific for diagnosing pancreatitis than amylase. Its levels tend to remain elevated for a longer period, sometimes up to 14 days, which can be useful if a patient presents late in the course of the disease. Amylase levels typically normalize more quickly, often within three to five days. Doctors frequently order both tests or may prefer a lipase test when assessing suspected pancreatic issues.