What is Hashimoto's (Hashimoto's thyroiditis)?

From the Guidelines

Hashimoto's thyroiditis is an autoimmune disorder that requires daily synthetic thyroid hormone replacement, typically with levothyroxine, to manage hypothyroidism and improve quality of life. The condition is characterized by chronic inflammation of the thyroid gland, leading to eventual hypothyroidism. According to the US Preventive Services Task Force recommendation statement 1, the principal treatment for hypothyroidism is oral T4 monotherapy (levothyroxine sodium).

Key Considerations

• The serum TSH test is the primary screening test for thyroid dysfunction, with multiple tests done over a 3- to 6-month interval to confirm or rule out abnormal findings 1.
• Follow-up testing of serum T4 levels in persons with persistently abnormal TSH levels can differentiate between subclinical (normal T4 levels) and “overt” (abnormal T4 levels) thyroid dysfunction 1.
• Treatment is generally recommended for patients with a TSH level that is undetectable or less than 0.1 mIU/L, particularly those with overt Graves disease or nodular thyroid disease 1.
• Patients should avoid taking calcium supplements, iron supplements, or antacids within 4 hours of levothyroxine as these can interfere with absorption.

Management and Monitoring

• Regular blood tests to monitor thyroid-stimulating hormone (TSH) levels are necessary, with target levels generally between 0.5-2.5 mIU/L, though this may vary based on individual factors.
• Medication dosage adjustments are common, especially during the first few months of treatment.
• Common symptoms of untreated Hashimoto's include fatigue, weight gain, cold intolerance, constipation, dry skin, and depression.

Research Gaps

• Although detection and treatment of abnormal TSH levels (with or without abnormal T4 levels) in asymptomatic persons is common practice, evidence that this clinical approach improves important health outcomes is lacking 1.
• Long-term randomized, blinded, controlled trials of screening for thyroid dysfunction would provide the most direct evidence on any potential benefits of this widespread practice.

From the Research

Hashimoto's Disease Overview

• Hashimoto's disease, also known as Hashimoto thyroiditis, is a common autoimmune disorder that affects the thyroid gland, leading to hypothyroidism 2.
• The disease is characterized by the presence of antibodies against thyroid peroxidase (TPOAbs), which can lead to the destruction of thyroid cells and a decrease in thyroid hormone production 2.
• Hashimoto's disease is more common in women than men, and its clinical presentation can vary from thyrotoxicosis to euthyroidism to hypothyroidism 2.

Diagnosis and Treatment

• The diagnosis of Hashimoto's disease is typically made through a combination of medical history, sonography, and blood analysis of thyroid function and thyroid antibodies 3.
• Levothyroxine (LT4) replacement therapy is the standard treatment for hypothyroidism caused by Hashimoto's disease, with the goal of normalizing thyroid-stimulating hormone (TSH) levels 4, 2, 5.
• The dose of LT4 used for treatment is based on the degree of preserved thyroid functionality and lean body mass, and usually ranges from 1.4 to 1.8 mcg/kg/day 2.

Challenges in Treatment

• Some patients with Hashimoto's disease may experience poor response to LT4 therapy despite normal TSH levels, due to factors such as co-morbidities, lack of vitamin and trace elements, and pharmacogenomic and pharmacokinetic factors 3.
• Ongoing symptoms despite LT4 treatment have led to some patients using alternative therapies, such as liothyronine or desiccated thyroid extract 5.
• Personalized thyroid hormone replacement therapy may be necessary to improve treatment outcomes in patients with Hashimoto's disease 6.

Complications and Associated Conditions

• Hashimoto's disease is associated with an increased risk of papillary thyroid cancer and thyroid lymphoma 2.
• The disease can also lead to extrathyroidal manifestations, such as psychiatric disorders, and may be associated with other autoimmune diseases 3.
• Malabsorption of LT4 can occur in patients with Hashimoto's disease, particularly those with comorbid gastrointestinal conditions such as gastroparesis and small intestinal bacterial overgrowth (SIBO) 4.