The connection between an underactive thyroid and stomach inflammation

Design: BOOST Thyroid.

Design: BOOST Thyroid.

Hashimoto’s, pernicious anemia, and autoimmune gastritis

An underactive thyroid (caused by Hashimoto’s) is sometimes diagnosed together with pernicious anemia and autoimmune gastritis (1). When this happens, doctors and scientists typically refer to this as polyglandular autoimmune syndrome (PAS). PAS occurs when more than one gland (an organ that secretes hormones or other substances) is affected by an autoimmune disease (2, 3).

Thyrogastric syndrome

Thyrogastric syndrome describes the connection between Hashimoto’s and chronic autoimmune gastritis (4).

4 in 10 people who have autoimmune gastritis have Hashimoto’s as well (5).

Autoimmune gastritis damages the stomach — causing iron deficiency, anemia, and at a later stage vitamin B deficiency and pernicious anemia. Pernicious anemia is a condition where red blood cell count is low because the intestine can’t absorb vitamin B12.

For people with an underactive thyroid who also have autoimmune gastritis, the body may not be able to fully absorb levothyroxine taken in pill form (5–7).

Commonalities between the thyroid and stomach

Both the thyroid and stomach are made from the same part of early embryo — the primitive gut — meaning their cells share similar properties. They both have specific structures on their surfaces that enable them to bring iodine into their cells.

Thyroid and stomach cells have some common functions:

  1. They transport iodine in and out of their cell — this helps build thyroid hormones and supports multiplying cells in the stomach (8).

  2. They both have peroxidase enzymes. In thyroid cells they are called thyroid peroxidase (TPO); in stomach cells they are called gastric peroxidase (GPO). Both provide cells with antioxidative properties.

  3. An overactive immune system leads to the destruction of both thyroid and stomach cells, as well as the forming of scar tissue (9, 10).

Autoimmune gastritis causes problems with the absorption of nutrients in the intestine, and can trigger the onset of anemia (low healthy red blood cell count) (11).

Hashimoto’s and anemia

If you have Hashimoto’s and anemia, your doctor might prescribe you iron supplements through pills. If your red blood cell count doesn’t improve after taking iron orally, it might be due to gastritis which prevents iron absorption (11).

Symptoms of gastritis develop slowly over the course of several years. All symptoms are caused by low levels of iron, vitamin B12, folate (vitamin B9), and other nutrients (12).

While iron deficiency leads to anemia, vitamin B12 deficiency leads to pernicious anemia. Both symptoms include (5):

  1. Weakness and fatigue

  2. Paresthesia (tingling, pricking, chilling, burning, or numb sensation on the skin with no apparent physical cause)

  3. Neuritis (inflammation of a peripheral nerve or nerves, usually causing pain and loss of function)

If you have autoimmune gastritis in addition to Hashimoto’s, your doctor might prescribe you liquid or softgel capsules of levothyroxine in order to make sure all of the levothyroxine reaches the intestine (13–16).

Track your medication, energy levels, and sleep in BOOST Thyroid app to understand if your symptoms are related to autoimmune gastritis.


  1. Centanni M, et al. Atrophic body gastritis in patients with autoimmune thyroid disease: an underdiagnosed association, 1999

  2. Kahaly GJ. Polyglandular autoimmune syndromes, 2009

  3. Fallahi P, et al. The association of other autoimmune diseases in patients with autoimmune thyroiditis: review of the literature and report of a large series of patients, 2016

  4. Doniach D, et al. Autoimmune phenomena in pernicious anaemia. Serological overlap with thyroiditis, thyrotoxicosis, and systemic lupus erythematosus, 1963

  5. Cellini M, et al. Hashimoto’s Thyroiditis and Autoimmune Gastritis, 2017

  6. Checchi S, et al. Prevalence of parietal cell antibodies in a large cohort of patients with autoimmune thyroiditis, 2010

  7. Lahner E, et al. Occurrence and risk factors for autoimmune thyroid disease in patients with atrophic body gastritis, 2008

  8. Portulano C, et al. The Na+/I- symporter (NIS): mechanism and medical impact, 2014

  9. Pearce EN, et al. Thyroiditis, 2003

  10. Neumann WL, et al. Autoimmune atrophic gastritis — pathogenesis, pathology and management, 2013

  11. Sibilla R, et al. Chronic unexplained anemia in isolated autoimmune thyroid disease or associated with autoimmune related disorders, 2008

  12. Toh BH. Diagnosis and classification of autoimmune gastritis, 2014

  13. Santaguida MG, et al. Thyroxine softgel capsule in patients with gastric-related T4 malabsorption, 2015

  14. Fallahi P, et al. Reversible normalisation of serum TSH levels in patients with autoimmune atrophic gastritis who received l-T4 in tablet form after switching to an oral liquid formulation: a case series, 2016

  15. Vita R, et al. Tablet levothyroxine (l-T4) malabsorption induced by proton pump inhibitor; a problem that was solved by switching to l-T4 in soft gel capsule, 2014

  16. Vita R, et al. Switching levothyroxine from the tablet to the oral solution formulation corrects the impaired absorption of levothyroxine induced by proton-pump inhibitors, 2014