Amylase

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Amylase is widely employed as a marker of acute pancreatitis and a significant elevation is diagnostic.

Physiology

α-amylase is a digestive enzyme that is predominantly secreted by the acinar cells of the exocrine pancreas. It is also secreted by the salivary glands. Pancreatic amylase is encoded by AMY2, and salivary amylase by AMY1, both genes on chromosome 1 ⁵.

The main function of the amylases is to initiate the digestion of complex polysaccharides, primarily starch, to their constituent simple sugars. This starts in the mouth with salivary α-amylase, which continues to work in the stomach (it is chemically protected from the gastric acid). In the small bowel, starting in the duodenum, pancreatic α-amylase digests the dietary carbohydrate, aided by remnant salivary α-amylase ³.

Starch is mainly composed of two glucose polymers: amylopectin (75%) and amylose (25%), and the main action of amylase is to break their internal α1,4 linkages. This results in the formation of oligosaccharides, which are primarily maltose, maltotriose, and α-limit dextrins ³.

Interpretation

The salivary glands and the pancreas account for most of the normal serum amylase found in a well individual ¹. These two amylase isoforms can be distinguished by laboratory assay. Normal serum amylase reference range is 19-86 units/litre ~~(U/L) - 86 U/L~~.

Compared to lipase, the other enzyme measured in suspected cases of acute pancreatitis, amylase has poorer sensitivity and is elevated for a shorter window of time ⁶. For this reason lipase is the preferred test for acute pancreatitis.

Causes of hyperamylasaemia

Amylase is found in small bowel intraluminal fluid and therefore bowel stasis can lead to abnormal absorption of the enzyme.

pancreatitis
other pancreatic assaults
- ERCP/EUS: instrumentation of the main pancreatic duct
- pancreatic trauma
bowel disease
- bowel ischaemia/infarction
- bowel perforation
salivary gland pathology
reduced homeostatic removal of amylase
- renal failure
- macroamylasaemia
chronic alcoholism
~~postsurgical~~post-surgical
- especially following coronary arterial bypass grafting (CABG)
lactic acidosis
eating disorders
- anorexia nervosa
- bulimia
ectopic amylase secretion by cancer
Gullo syndrome

Causes of hypoamylasaemia

The main cause of a low serum amylase is chronic pancreatitis ⁴.

Rare individuals/families with isolated pancreatic amylase deficiency have been seen. They exhibit signs and symptoms of carbohydrate malabsorption.

-<p><strong>Amylase</strong> is widely employed as a marker of <a href="/articles/acute-pancreatitis">acute pancreatitis</a> and a significant elevation is diagnostic. </p><h4>Physiology</h4><p>α-amylase is a digestive enzyme that is predominantly secreted by the acinar cells of the exocrine pancreas. It is also secreted by the salivary glands. Pancreatic amylase is encoded by <em>AMY2</em>, and salivary amylase by <em>AMY1</em>, both genes on chromosome 1 <sup>5</sup>.</p><p>The main function of the amylases is to initiate the digestion of complex polysaccharides, primarily starch, to their constituent simple sugars. This starts in the mouth with salivary α-amylase, which continues to work in the stomach (it is chemically protected from the gastric acid). In the small bowel, starting in the duodenum, pancreatic α-amylase digests the dietary carbohydrate, aided by remnant salivary α-amylase <sup>3</sup>.</p><p>Starch is mainly composed of two glucose polymers: amylopectin (75%) and amylose (25%), and the main action of amylase is to break their internal α1,4 linkages. This results in the formation of oligosaccharides, which are primarily maltose, maltotriose, and α-limit dextrins <sup>3</sup>.</p><h4>Interpretation</h4><p>The salivary glands and the pancreas account for most of the normal serum amylase found in a well individual <sup>1</sup>. These two amylase isoforms can be distinguished by laboratory assay. Normal serum amylase reference range is 19 units/litre (U/L) - 86 U/L.</p><h4>Causes of hyperamylasaemia</h4><p>Amylase is found in small bowel intraluminal fluid and therefore bowel stasis can lead to abnormal absorption of the enzyme. </p><ul>
+<p><strong>Amylase</strong> is widely employed as a marker of <a href="/articles/acute-pancreatitis">acute pancreatitis</a> and a significant elevation is diagnostic.</p><h4>Physiology</h4><p>α-amylase is a digestive enzyme that is predominantly secreted by the acinar cells of the exocrine pancreas. It is also secreted by the salivary glands. Pancreatic amylase is encoded by <em>AMY2</em>, and salivary amylase by <em>AMY1</em>, both genes on chromosome 1 <sup>5</sup>.</p><p>The main function of the amylases is to initiate the digestion of complex polysaccharides, primarily starch, to their constituent simple sugars. This starts in the mouth with salivary α-amylase, which continues to work in the stomach (it is chemically protected from the gastric acid). In the small bowel, starting in the duodenum, pancreatic α-amylase digests the dietary carbohydrate, aided by remnant salivary α-amylase <sup>3</sup>.</p><p>Starch is mainly composed of two glucose polymers: amylopectin (75%) and amylose (25%), and the main action of amylase is to break their internal α1,4 linkages. This results in the formation of oligosaccharides, which are primarily maltose, maltotriose, and α-limit dextrins <sup>3</sup>.</p><h4>Interpretation</h4><p>The salivary glands and the pancreas account for most of the normal serum amylase found in a well individual <sup>1</sup>. These two amylase isoforms can be distinguished by laboratory assay. Normal serum amylase reference range is 19-86 units/litre.</p><p>Compared to <a title="Lipase" href="/articles/lipase">lipase</a>, the other enzyme measured in suspected cases of acute pancreatitis, amylase has poorer sensitivity and is elevated for a shorter window of time <sup>6</sup>. For this reason lipase is the preferred test for acute pancreatitis.</p><h4>Causes of hyperamylasaemia</h4><p>Amylase is found in small bowel intraluminal fluid and therefore bowel stasis can lead to abnormal absorption of the enzyme. </p><ul>
~~-<li>postsurgical<ul><li>especially <a href="/articles/cabg">coronary arterial bypass grafting (CABG)</a>~~
+<li>post-surgical<ul><li>especially following <a href="/articles/cabg">coronary arterial bypass grafting (CABG)</a>
-</ul><h4>Causes of hypoamylasaemia</h4><p>The main cause of a low serum amylase is <a href="/articles/chronic-pancreatitis-2">chronic pancreatitis</a> <sup>4</sup>.</p><p>Rare individuals/families with isolated pancreatic amylase deficiency have been seen. They exhibit signs and symptoms of carbohydrate malabsorption. </p>
+</ul><h4>Causes of hypoamylasaemia</h4><p>The main cause of a low serum amylase is <a href="/articles/chronic-pancreatitis-2">chronic pancreatitis</a> <sup>4</sup>.</p><p>Rare individuals/families with isolated pancreatic amylase deficiency have been seen. They exhibit signs and symptoms of carbohydrate malabsorption.</p>

References changed:

6. Ismail OZ, Bhayana V. Lipase or amylase for the diagnosis of acute pancreatitis?. (2017) Clinical biochemistry. 50 (18): 1275-1280. <a href="https://doi.org/10.1016/j.clinbiochem.2017.07.003">doi:10.1016/j.clinbiochem.2017.07.003</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/28720341">Pubmed</a> <span class="ref_v4"></span>