HASHIMOTO`S THYROIDITIS

What is Hashimoto`s thyroiditis?

The thyroid is a small, butterfly-shaped gland in the front of your neck. Hashimoto thyroiditis (HT), also known as chronic autoimmune thyroiditis or chronic lymphocytic thyroiditis, is an autoimmune disease that leads to the destruction of thyroid follicular cells through immune-mediated processes. As a result, large numbers of white blood cells which are part of the immune system, build up in the thyroid eventually causing fibrosis and dysfunction of the gland. 

This condition was initially described by a Japanese physician, Haruto Hashimoto, in 1912 as "struma lymphomatosa" after he found enlarged thyroids having lymphocytic infiltration.

Who gets HT?

Women are more commonly affected. The female-to-male ratio is at least 7 to 10:1. The incidence of HT increases with age, with most cases found between ages 45 and 55 years. The incidence tends to be higher in countries with a lower prevalence of iodine deficiency. HT can occur alone, or it can occur as a part of autoimmune polyglandular syndrome (APS). Some individuals with Graves disease might transform into HT and vice versa. This could indicate a common pathogenesis for these disorders but different clinical presentations.

Almost 10% of the population in the United States has been shown to have positivity for thyroid antibodies. HT is the most common cause of hypothyroidism in the United States and in those areas of the world where dietary iodine intake is adequate. A systematic review and meta-analysis, including studies from multiple countries, found the overall global prevalence of HT to be 7.5%, higher in low-middle-income areas at 11.4%. Additionally, the prevalence in women was 4 times that in men. (https://www.ncbi.nlm.nih.gov/books/NBK459262/) 

What are the causes of HT?

What causes the immune system to attack thyroid cells is not clear, however disease onset may be related to: 

• Genetic factors
• Environmental triggers, such as infection, stress or radiation exposure
• Interactions between environmental and genetic factors

People with following conditions are at an increased risk of getting Hashimoto's thyroiditis:

• Women are much more likely to get HT.
• HT can occur at any age but more commonly occurs during middle age.
• Having another autoimmune disease — such as rheumatoid arthritis, type 1 diabetes or lupus.
• Having a family history thyroid disorders or other autoimmune diseases.
• Typical changes in immune function during pregnancy may be a factor in HT that begins after pregnancy.
• Too much iodine in the diet may function as a trigger among people already at risk for HT.
• People exposed to excessive levels of environmental radiation are more prone to HT. (https://www.mayoclinic.org/diseases-conditions/hashimotos-disease/symptoms-causes/syc-20351855) 
• There are some studies linking deficiencies of Selenium, Iron and Vitamin D with developing thyroid dysfunction. (https://www.ncbi.nlm.nih.gov/books/NBK459262/)  

What are the symptoms of HT?

Goitre is a first common sign which appears in HT, with enlargement of the thyroid gland. It can create a feeling of fullness in your lower neck with appearance of swelling. With further disease progression, hypothyroidism can cause following symptoms over time: 

• Mild weight gain
• Constipation
• Dry skin
• Feeling cold
• Slower-than-normal heart rate (bradycardia)
• Joint stiffness and muscle pain
• Dry, brittle hair; slow hair growth or hair loss
• Low or depressed mood
• Puffy eyes and face
• Memory problems or difficulty concentrating
• Heavy or irregular periods
• Decreased libido
• Female or male infertility 
• Brittle nails 
• Enlargement of the tongue (https://my.clevelandclinic.org/health/diseases/17665-hashimotos-disease) 

Tiredness, fatigue, lethargy and excessive sleeping

How is HT diagnosed? 

• TSH test: Thyroid stimulating hormone (TSH) is produced by the pituitary gland. When the pituitary detects low thyroid hormones in the blood, it sends thyroid-stimulating hormone (TSH) to the thyroid to prompt an increase in thyroid hormone production. High TSH levels in the blood indicates hypothyroidism.
• T-4 test: The main thyroid hormone is thyroxine (T-4). A low blood level of thyroxine (T-4) confirms the findings of a TSH test and indicates the problem is within the thyroid itself.
• Antibody test: Usually in Hashimoto's disease, the immune system produces an antibody to thyroid peroxidase (TPO), a protein that plays an important part in thyroid hormone production. Most people with Hashimoto's disease will have thyroid peroxidase (TPO) antibodies in their blood. Lab tests for other antibodies associated with Hashimoto's disease may need to be done. (https://www.mayoclinic.org/diseases-conditions/hashimotos-disease/diagnosis-treatment/drc-20351860) 

How is HT treated? 

Not everyone with Hashimoto’s disease develops hypothyroidism. The mainstay of treatment for hypothyroidism that develops due to Hashimoto thyroiditis is thyroid hormone replacement.

• A study including 412 individuals showed an improvement in quality-of-life parameters with selenium supplementation (200 µg/daily) in individuals on levothyroxine for management of hypothyroidism due to HT. 
• Every unit increase in iron level has been demonstrated to decrease the risk of Hashimoto thyroiditis by 43% in women of reproductive age.
• A systematic review and meta-analysis including 862 individuals also showed the positive effect of vitamin D supplementation on thyroid function and reduction in antibody levels. (https://www.ncbi.nlm.nih.gov/books/NBK459262/) 

Titrated levothyroxine sodium has a half life of 7 days and is typically prescribed to be taken once per day orally. It is best taken early in the morning on an empty stomach for optimum absorption, should not be taken with iron or calcium supplements, aluminium hydroxide, and proton pump inhibitors to avoid suboptimal absorption. 

 There is little evidence supporting the role of alternative therapies to regulate immune function. Strong evidence supports the role of balanced diet, adequate sleep, regular exercise and managing stress for helping alleviate symptoms and coping with hypothyroidism.