The connection between an underactive thyroid and stomach inflammation
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 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:
They transport iodine in and out of their cell — this helps build thyroid hormones and supports multiplying cells in the stomach (8).
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.
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):
Weakness and fatigue
Paresthesia (tingling, pricking, chilling, burning, or numb sensation on the skin with no apparent physical cause)
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.
Centanni M, et al. Atrophic body gastritis in patients with autoimmune thyroid disease: an underdiagnosed association, 1999
Kahaly GJ. Polyglandular autoimmune syndromes, 2009
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
Doniach D, et al. Autoimmune phenomena in pernicious anaemia. Serological overlap with thyroiditis, thyrotoxicosis, and systemic lupus erythematosus, 1963
Cellini M, et al. Hashimoto’s Thyroiditis and Autoimmune Gastritis, 2017
Checchi S, et al. Prevalence of parietal cell antibodies in a large cohort of patients with autoimmune thyroiditis, 2010
Lahner E, et al. Occurrence and risk factors for autoimmune thyroid disease in patients with atrophic body gastritis, 2008
Portulano C, et al. The Na+/I- symporter (NIS): mechanism and medical impact, 2014
Pearce EN, et al. Thyroiditis, 2003
Neumann WL, et al. Autoimmune atrophic gastritis — pathogenesis, pathology and management, 2013
Sibilla R, et al. Chronic unexplained anemia in isolated autoimmune thyroid disease or associated with autoimmune related disorders, 2008
Toh BH. Diagnosis and classification of autoimmune gastritis, 2014
Santaguida MG, et al. Thyroxine softgel capsule in patients with gastric-related T4 malabsorption, 2015
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
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
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