Hashimoto's Thyroiditis

What is Hashimoto’s thyroiditis (HT)?

HT is a thyroid autoimmune disease, whereby the body’s immune system mistakenly attacks the thyroid tissue. The thyroid is a butterfly-shaped gland located in the lower neck, responsible for producing hormones that play a vital role in regulating metabolism. HT disproportionally affects women, estimated to be diagnosed 10 times more vs men [1].

HT is the most common cause of hypothyroidism

The autoimmune attack in HT causes deterioration of the thyroid gland. Bouts of the thyroid hormone, thyroxine (T4) can be released, resulting in temporary periods of hyperthyroidism. As the thyroid loses its function, insufficient amounts of T4 are produced, resulting in hypothyroidism. It is estimated that 2% of the UK population have hypothyroidism of which HT is the most common cause [2]. HT becomes more prevalent with age, peaking in women between 30 and 50 years of age [1], and is thought to increase the risk of developing other autoimmune diseases, and thyroid cancer [3].

Symptoms of HT

Swelling of the thyroid, known as a goitre, is a common first symptom of HT. Symptoms of hypothyroidism, resulting from untreated HT, include [3]:

  • Constant fatigue
  • Cold extremities
  • Weight gain or loss
  • Brain fog
  • Memory loss
  • Dry skin
  • Hair loss
  • Disturbances in bowel movements
  • Depression 
  • Muscle aches

Symptoms can be broad, and none are unique to HT. Some people may feel normal, while others experience debilitating symptoms. Consequently, symptoms are often overlooked or attributed to feeling “under the weather” or just a part of “getting older”. It is estimated that up to 5% of the population in Europe has undiagnosed thyroid failure [4].

If left untreated, hypothyroidism caused by HT can have serious complications, including heart failure and myxoedema coma — a life-threatening condition that occurs with extreme hypothyroidism [5].

How does HT affect women?

As the thyroid gland plays an important role in regulating the female reproductive system, symptoms of HT in women include [6]:

  • Irregular menstruation or absence of menstruation (known as amenorrhea)
  • Difficulty getting pregnant/ infertility
  • Increased risk of cyst development in the ovaries

Normal pregnancy symptoms, such as weight gain and fatigue, can also mask thyroid problems [6]. Left untreated, HT in pregnant women can increase chances of [6]:

  • Preeclampsia
  • Anaemia
  • Miscarriage
  • Placental abruption
  • Postpartum bleeding
  • Premature birth
  • Low birth weight
  • Stillbirth

How is HT diagnosed?

Diagnosis of HT is based on symptoms, thyroid examination, and blood test results [1]. Physical examination of the thyroid detects signs of swelling or enlargement. A thyroid ultrasound may also be performed to detect the presence of any abnormal regions of growth, known as nodules. Elevated thyroid-stimulating hormone (TSH), which indicates that the pituitary gland is trying to stimulate the thyroid gland to produce more T4, is typically associated with hypothyroidism and HT. Elevated TSH results are typically followed by testing of T4, which, when too low, indicates hypothyroidism. As HT is an autoimmune disease, the body produces abnormal antibodies, such as those which target thyroid peroxidase (TPO antibodies), an important enzyme involved in thyroid hormone production. Therefore, testing for the presence of TPO antibodies may be used to confirm that HT is the cause of hypothyroidism.

What causes HT?

Although the exact cause is unknown, HT is thought to arise from genetic susceptibility combined with an environmental trigger. A variety of possible environmental triggers exist, including a high-stress lifestyle, malnutrition, a viral or bacterial infection, excessive iodine, smoking, exposure to heavy metals, and endocrine disruptors (chemicals that interfere with hormone production) [7]. Immune changes during pregnancy can also trigger HT [8]. More recently, it has been proposed that impaired gut microbiota and intestinal permeability or a ‘leaky gut’, a condition whereby bacteria and toxins can ‘leak’ through the intestinal wall, may play a role in triggering HT [9].

Current treatment

Treatment involves supplementation of the thyroid hormone with the oral medication levothyroxine, which very rarely has side effects if the correct dose is taken. Women with HT may require a higher dose during pregnancy to support the development of the foetus. Most people with HT will require lifelong treatment.

Hyperthyroid symptoms, such as palpitations, weight loss, and anxiety, occur if the dose is too high, and hypothyroid symptoms continue if the dose is too low. Therefore, it is important to have regular blood tests, particularly when first starting to take the medication, to monitor whether the dose is optimal. However, levothyroxine doesn’t work for everyone. This can be due to difficulties with the conversion of levothyroxine, which consists of T4, to the active form of Triiodothyronine (T3) [10]. In these cases, combination therapy with levothyroxine and triiodothyronine (T3) may be more effective [8, 10].

Is there a cure for HT?

Despite medication stabilising T4 levels in most cases, this does not stop the autoimmune attack of the thyroid. Moreover, even when normalised TSH levels are achieved with levothyroxine therapy, around 5–10% of patients continue to live with HT symptoms [10]. However, a growing body of research suggests that symptoms can be alleviated, and autoimmune activity may be reduced through lifestyle interventions.

Gluten

Gluten may trigger autoimmune activity, and coeliac disease, the autoimmune condition whereby the body attacks its own tissues in response to gluten, is 10-fold more common in people with HT compared to the healthy population [11, 12]. Therefore, eliminating gluten may help reduce autoimmune activity and alleviate symptoms. Diagnostic tests can be performed to identify gluten intolerance or insensitivity.

Lactose

It is estimated that 75% of patients with HT are lactose intolerant [13]. Moreover, lactose intolerance can reduce the bioavailability of levothyroxine, thereby enforcing the use of higher doses. Therefore, it may be advised for people living with HT to take a lactose tolerance test and eliminate lactose, if necessary.

Stress

Often overlooked, mental health may have a large impact on the onset and development of HT. Chronic stress has a major influence on the body, including the proper functioning of the immune system [14]. In contrast to other autoimmune diseases, research on the relationship between stress and HT is lacking [7].

Glutathione

People with HT often have lower antioxidant levels and an impaired ability to clear out toxins [15]. The level of glutathione, the most important antioxidant in the body, was found to be 60% lower in people with HT compared to healthy people [16]. It has been suggested that glutathione supplementation may help reduce autoimmune activity [7].

Nutrients

Those with HT are also often found to be deficient in one or several minerals such as iron, zinc, copper, magnesium, potassium, selenium, thiamine, vitamins A, C, D, and B6, many of which are important for thyroid hormone synthesis and regulation [9]. Selenium and zinc are required for the conversion of T4 to the active T3 form, and vitamin D is involved in immune response regulation [9]. Therefore, people with HT may be advised to get tested for these deficiencies and supplement accordingly, ideally after consulting a nutritionist.

Gut microbiota

Patients with HT often have an imbalanced gut microbiome, known as gut dysbiosis, which may stimulate autoimmune processes [9]. The composition of the gut microbiota also influences the availability of micronutrients which are essential for the thyroid gland [9]. To improve gut microbiota, it is recommended to eat a variety of fibre-rich foods including fruit, veg, and whole grains [9].

Summary and future research

HT is a thyroid autoimmune disease, particularly prevalent in women. Left untreated, HT can have serious implications, including women’s reproductive health. An emerging body of research highlights the importance of lifestyle factors, particularly nutrition and food intolerances, in regulating and even reducing autoimmune activity in HT. This has great potential for empowering people with HT to take control of the disease and improve their health. However, data is still lacking in this area and the mechanisms are not well understood. Further research with larger-scale, randomised control studies that are inclusive of women, are needed to understand the impact of factors such as diet and stress on the disease activity of HT. This may enable the development of personalised treatment regimens for people living with HT.

References

  1. Mincer DL, Jialal I. Hashimoto Thyroiditis. In: StatPearls. StatPearls Publishing; 2021. Accessed December 6, 2021. http://www.ncbi.nlm.nih.gov/books/NBK459262/
  2. Context | Thyroid disease: assessment and management | Guidance | NICE. Accessed February 8, 2022. https://www.nice.org.uk/guidance/ng145/chapter/Context
  3. What Is Hashimoto’s Thyroiditis? EndocrineWeb. Accessed December 28, 2021. https://www.endocrineweb.com/conditions/hashimotos-thyroiditis
  4. Garmendia Madariaga A, Santos Palacios S, Guillén-Grima F, Galofré JC. The incidence and prevalence of thyroid dysfunction in Europe: a meta-analysis. J Clin Endocrinol Metab. 2014;99(3):923-931. doi:10.1210/jc.2013-2409
  5.  Hashimoto Disease. Accessed December 14, 2021. https://www.hormone.org/diseases-and-conditions/hashimoto-disease
  6. Hashimoto’s disease. Accessed February 16, 2022. https://www.womenshealth.gov/a-z-topics/hashimotos-disease
  7. Ihnatowicz P, Drywień M, Wątor P, Wojsiat J. The importance of nutritional factors and dietary management of Hashimoto’s thyroiditis. Ann Agric Environ Med. 2020;27(2):184-193. doi:10.26444/aaem/112331
  8.  Chiovato L, Magri F, Carlé A. Hypothyroidism in Context: Where We’ve Been and Where We’re Going. Adv Ther. 2019;36(Suppl 2):47-58. doi:10.1007/s12325-019-01080-8
  9. Knezevic J, Starchl C, Tmava Berisha A, Amrein K. Thyroid-Gut-Axis: How Does the Microbiota Influence Thyroid Function? Nutrients. 2020;12(6):1769. doi:10.3390/nu12061769
  10. Wiersinga WM, Duntas L, Fadeyev V, Nygaard B, Vanderpump MPJ. 2012 ETA Guidelines: The Use of L-T4 + L-T3 in the Treatment of Hypothyroidism. Eur Thyroid J. 2012;1(2):55-71. doi:10.1159/000339444
  11. Ozkan C, Yetkin I. Celiac disease and autoimmune thyroid diseases. Med Sci Int Med J. 2016;5(4):1055. doi:10.5455/medscience.2016.05.8461
  12. Sharma BR, Joshi AS, Varthakavi PK, Chadha MD, Bhagwat NM, Pawal PS. Celiac autoimmunity in autoimmune thyroid disease is highly prevalent with a questionable impact. Indian J Endocrinol Metab. 2016;20(1):97-100. doi:10.4103/2230-8210.172241
  13. Asik M, Gunes F, Binnetoglu E, et al. Decrease in TSH levels after lactose restriction in Hashimoto’s thyroiditis patients with lactose intolerance. Endocrine. 2014;46(2):279-284. doi:10.1007/s12020-013-0065-1
  14. Liu YZ, Wang YX, Jiang CL. Inflammation: The Common Pathway of Stress-Related Diseases. Front Hum Neurosci. 2017;11:316. doi:10.3389/fnhum.2017.00316
  15. Ruggeri RM, Vicchio TM, Cristani M, et al. Oxidative Stress and Advanced Glycation End Products in Hashimoto’s Thyroiditis. Thyroid. 2016;26(4):504-511. doi:10.1089/thy.2015.0592
  16. Rostami R, Aghasi MR, Mohammadi A, Nourooz-Zadeh J. Enhanced oxidative stress in Hashimoto’s thyroiditis: Inter-relationships to biomarkers of thyroid function. Clin Biochem. 2013;46(4):308-312. doi:10.1016/j.clinbiochem.2012.11.021
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