Amylase is a digestive enzyme that functions primarily in the digestion of complex carbohydrates. It is primarily formed by the pancreas and salivary glands, but is also present in other tissues including:
- Fallopian tube
- Lungs
- Thyroid
- Tonsils
- Various malignant neoplasms
The pancreatic and the salivary isoenzymes are the ones most commonly detected by the assay.
Serum amylase assays have the following clinical utility:
- Aid in the diagnosis of acute pancreatitis
- Aid in the diagnosis of macroamylasemia
- Aid in the diagnosis of pancreatic duct obstruction
- Detect injury to the pancreas due to blunt trauma or surgery
- Exclude acute pancreatitis as a cause of acute abdominal pain
Additional information:
- In early acute pancreatitis, serum amylase levels start increasing 6-24 hours after onset. It often decreases after 3-7 days due to increased renal amylase excretion (Lipase will be useful in these situations).
- When normal amylase combines with high molecular weight protein immunoglobulin, macroamylase is formed which is characterized by high serum amylase
- Pancreatic amylase is tightly bound to the mucosa of the small intestine. Small bowel injury is often associated with elevated serum amylase.
- Patients with elevated serum amylase, in the absence of signs of pancreatic diseases, should undergo screening for celiac disease.
- When routine monitoring is being performed, the patient should abstain from alcohol for at least 24 hours before the test (alcohol consumption may result in elevations).
- For at least 2 hours before the test, no food or fluids, except water, should be taken.
Overview:
- In neonates, usually no amylase activity is detected.
- At about 2 months of age, measurable amylase activity is detected. It increases gradually and reaches adult values by age of 1 year.
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
Conv. units
(U/L) | SI units
(µKat/L) |
|---|
| 20-110 | 0.33-1.85 |
High serum amylase concentration is called hyperamylasemia. It may occur in the following conditions:
- Increase in pancreatic amylase
- Pancreatic diseases
- Acute Pancreatitis
- Biliary Tract Disease
- Choledocholithiasis
- Chronic Pancreatitis
- Early Cystic Fibrosis
- Pancreatic Ascites
- Pancreatic Abscess
- Pancreatic Cancer
- Pancreatic Trauma
- Post ERCP
- Pseudocyst
- Gut diseases
- Appendicitis
- Celiac Disease
- Gastric Resection
- Intestinal Obstruction
- Mesenteric Infarct
- Perforated Bowel
- Peritonitis
- Other
- Increase in salivary amylase
- Salivary diseases
- Female Genital tract
- Malignancies
- Ectopic production (especially esophagus, lungs and ovary)
- Other
- Increase in both salivary and pancreatic isoenzymes
- Liver diseases
- Renal Failure
- Increase in either salivary or pancreatic isoenzyme
- Alcoholism
- Others
- Ketoacidosis
- Extracorporeal Circulation
- Increase in macroamylase
- Macroamylasemia (high serum amylase but low urine amylase)
Drugs that increase the serum amylase levels include:
- Asparaginase
- Aspirin
- Azathioprine
- Captopril
- Cholinergic agents
- Cimetidine
- Clofibrate
- Corticosteroids
- Diuretics (Loop & Thiazide)
- Estrogens
- Ethacrynic acid
- Ibuprofen
- Indomethacin
- Methyldopa
- Nitrofurantoin
- Opiates
- Oral contraceptives
- Pentamidine
- Pentazocine
- Sulfonamides
- Tetracycline
- Valproic acid
- Zalcitabine
Normal or high serum amylase levels may be seen in:
- Relapsing or chronic pancreatitis
- Alcoholism
- Pregnancy
Low levels of serum amylase may be seen in the following conditions
- Cystic fibrosis (advanced)
- Eclampsia
- Hepatic disease or Cirrhosis
- Hypertriglyceridemia (may be falsely low)
- Pancreatic cancer
- Pancreatectomy
- Pancreatic insufficiency
- Renal disease
Drugs that decrease the serum amylase levels include:
- Anabolic steroids
- Citrates
- Fluorides
- Oxalates