Lab Testing and Hashimoto Thyroiditis

The most common cause of thyroiditis (thyroid gland inflammation) is Hashimoto thyroiditis. In the US, it is also the most common cause of hypothyroidism (underactive thyroid). An autoimmune disorder is what causes Hashimoto thyroiditis.  

The thyroid is a small butterfly-shaped gland that lies flat on the base of the throat against the windpipe. It produces triiodothyronine (T3 and thyroxine (T4), which are hormones that play an essential role in controlling metabolism, or the rate at which the body uses energy.  

The natural defenses of the body (immune system) normally protect you against foreign invaders, like bacteria and viruses, through recognizing and removing antibodies. Hashimoto thyroiditis causes the immune system to produce autoantibodies against the own organs and tissues of the body that attack your thyroid gland. That damages it so that it cannot produce enough thyroid hormone, which leads to hypothyroidism symptoms. The thyroid may become rubbery, firm, and enlarged (a goiter), but usually is not tender.   

Hashimoto thyroiditis occurs in the United States at a rate of 0.8 per 1,000 men a year and 3.5 per 1,000 women a year. People of any age can be affected, but it occurs most frequently in women 30 to 50 years old. Women are 10 to 15 times more likely than men to get Hashimoto thyroiditis.  

People who have thyroid diseases in their family history or who have a different autoimmune disease like lupus, pernicious anemia, celiac disease, rheumatoid arthritis, adrenal insufficiency, or type 1 diabetes, have an increased risk to develop Hashimoto thyroiditis. 

Symptoms and Signs  

A person with Hashimoto thyroiditis might not show any symptoms or signs for several years. However, eventually, the individual might experience some hypothyroidism that, over time, will worsen.  

Symptoms and signs can include the following:  

  • Increased risk for pregnant women to miscarriage 
  • Weight gain 
  • Difficulty swallowing and/or voice hoarseness  
  • Thinning hair 
  • Muscle weakness 
  • Joint and muscle pain 
  • Menstrual irregularities, excessive and heavy bleeding  
  • Cold intolerance 
  • Forgetfulness 
  • Tiredness, fatigue 
  • Dry skin 
  • Depression  
  • Constipation 

 Laboratory Tests 

Tests are conducted to evaluate your thyroid’s health, monitor treatment, and diagnose Hashimoto thyroiditis.   

One or more blood tests might be conducted to determine whether your thyroid is functioning correctly and to monitor hormone production and thyroid function: 

Thyroid-stimulating hormone (TSH) – in hypothyroidism, typically it is elevated  

Free T4 – in hypothyroidism, often it is decreased 

Free or Total T3 – decreased sometimes but might be within the normal reference ranging, so it is less useful compared to the free T4 test. 

Other tests might be ordered for helping to diagnose Hashimoto thyroiditis and for detecting autoantibodies being directed against your thyroid.  

Anti-thyroid peroxidase antibody test (anti-TPO) – autoantibodies are detected by the test that targets a protein that is contained within thyroid cells. Most individuals who have Hashimoto thyroiditis also have those antibodies, and individuals with hypothyroidism that is caused by another condition do not. However, certain people who do not have hypothyroidism may have those antibodies as well. 

Antithyroglobulin antibody (TgAb) – Autoantibodies against thyroglobulin are detected by this test, which is the storage type of thyroid hormone. When the test has a positive result, it can be an indication of Hashimoto thyroiditis. Although thyroglobulin antibodies are frequently positive, they still are not as specific or sensitive as anti-TPO. Therefore, they are not ordered frequently.  

If your Hashimoto thyroiditis is a mild form, your blood might not contain thyroid antibodies.