The enzyme amylase originates in either the pancreas or salivary glands and aids the body’s digestive process. Pancreatic amylase is secreted through the pancreatic duct into the duodenum and its primary function is to break down fats, proteins and carbohydrates as a first step in the digestion process. Amylase produced by the salivary glands helps convert starches into complex sugars such as dextrose. Other tissues may also exhibit some amylase activity, including the ovaries, fallopian tubes, small and large intestine, liver, placenta and skeletal muscle. Amylase enzyme levels increase when these glands are inflamed or obstructed.
Amylase is usually present in the blood and urine in small quantities. Levels have been shown to increase in blood and urine after pancreatic cell injury (pancreatitis), in pancreatic duct obstructions (gallstones, or rarely with obstruction by pancreatic tumor) and in some genetic disorders that affect pancreatic function such as cystic fibrosis.
The primary use of total serum amylase is in the diagnosis of acute pancreatitis. In this disorder, serum amylase begins to rise within 2 to 12 hours of onset of symptoms, with peak levels occurring in 12 to 72 hours, and levels returning to normal usually within 4 days. Elevations of 4 to 6 times normal are usual, but some patients show lesser elevation and a few show no elevation. Serum amylase levels do not correlate with the severity of illness and a return to normal is not always an indicator of resolution of illness. In patients with hyperlipidemia the amylase levels may be normal; this can be approached by ultracentrifugation of the specimen or serial dilutions. Amylase is not specific to the pancreas or pancreatitis. Elevated levels can be seen in diseases such as ectopic pregnancy, intestinal diseases, salivary gland disease and mumps.