Achlorhydria, Causes of Low or No Stomach Acid

What is achlorhydria?

Achlorhydria is the medical term for a lack of stomach acid (hydrochloric acid) due to the failure of the parietal cells to produce gastric acid. Hypochlorhydria is the term for diminished secretion of stomach acid. Achlorhydria may also be referred to as gastric anacidity. Hydrochloric acid (HCl) is not the only component of gastric juices so in achlorhydria, there is still gastric juice but it is absent of HCl.

Achlorhydria can be defined by :

  • A detectable change in pH, broadly above 6.5, but more specifically as a pH > 5.09 (men) and >6.81 (women).
  • Reduced acid output – a maximal acid output (MAO) < 6.9 mmol/h (men) and 5 mmol/h (women).
  • A reduction in the conversion of pepsinogen into pepsin as this requires HCl.

Causes of Low or No Gastric Acid

It is important to understand the process of gastric acid secretion and the mechanisms by which it is produced, stimulated and inhibited.

  • Gastric atrophy
  • This is a result of chronic inflammation of the gastric mucosa and there is a loss of glandular gastric cells.
  • Causes
    • Chronic gastritis usually due to H.pylori infection.
    • Autoimmune gastritis as a result of antibodies against the parietal cells – this may be seen in pernicious anemia.
  • Helicobacter pylori infection
  • Causes of Low/No Stomach Acid
    • Proinflammatory chemicals due to H.pylori infection suppresses the enterochromaffin-like cells (ECL) which stimulate HCl secretion by the action of histamine.
    • Untreated H.pylori infection can result in chronic gastritis, which may lead to gastric atrophy (explained above).
  • Drugs
  • Long term use or excessive use of the following drugs may result in iatrogenic achlorhydria.
  • Proton Pump Inhibitors (PPI’s)
    • These drugs work by disrupting the H+/K+ ATPase enzyme system which is responsible for transporting hydrogen ions into the oxyntic gland canaliculus and the subsequent production of HCl.
  • Histamine H2-Receptor Antagonist
    • Also known as H2 blockers, these drugs prevent the action of histamine secreted by ECL cells on the parietal cells which produce HCl.
  • Tumors
  • Gastric cancer
    • Tumors that affect the fundus of the stomach are more likely to result in achlorhydria as it destroys the parietal cells which are responsible for the secretion of HCl.
  • VIPoma
    • This is a tumor of the pancreas which causes the cells to secrete excess amounts of vasoactive intestinal peptide (VIP) which inhibits gastric acid.
  • Somatostatinoma
    • This is a tumor that is primarily found in the pancreas and can simultaneously inhibit secretion of VIP and gastrin and increase secretion of these hormones. Low gastrin = low gastric acid. High VIP = low gastric acid.
  • Surgery
  • Gastric resection for the treatment of certain stomach conditions, like antrectomy, or certain types of weight loss surgery. This includes :
    • Roux-en-Y gastric bypass surgery
    • Gastric reduction duodenal switch
  • Menetrier Disease
  • Enlargement of the ridges of the stomach wall (rugae) and reduction in the amount of parietal cells that are responsible for gastric acid secretion.
  • Causes :
    • The exact cause is unknown but it may be linked to genetic factors.
  • Mucolipidosis type IV
  • This is an inherited disorder that impairs the production of stomach acid.
  • Other causes
  • Radiation therapy involving the stomach.
  • Age related changes
  • Vagotomy


  1. Achlorhydria. Emedicine

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