What is Hashimoto's disease?

Hashimoto's Thyroiditis: An Overview

Hashimoto's thyroiditis is the most common autoimmune thyroid disorder and the leading cause of hypothyroidism in industrialized nations, characterized by chronic autoimmune destruction of the thyroid gland that often leads to progressive thyroid dysfunction. 1, 2

Definition and Pathophysiology

Hashimoto's thyroiditis (HT), also known as chronic lymphocytic thyroiditis, develops due to:

• Genetic susceptibility modulated by environmental factors
• Imbalance in self-tolerance mechanisms
• Thyroid infiltration by lymphocytes (especially T cells)
• Antibody-mediated autoimmune response through thyroid peroxidase antibodies (TPOAbs)
• Progressive destruction of thyrocytes leading to thyroid atrophy and fibrosis 2

Clinical Presentation

Hashimoto's thyroiditis can present in three distinct clinical phases:

1. Thyrotoxicosis (Hashitoxicosis) - When stored thyroid hormones are released into circulation from destroyed thyroid follicles
2. Euthyroidism - When preserved thyroid tissue compensates for destroyed thyrocytes
3. Hypothyroidism - When thyroid hormone production becomes insufficient 2

Common Symptoms of Hypothyroidism

• Fatigue
• Muscle cramps
• Constipation
• Cold intolerance
• Hair loss
• Voice changes
• Weight gain
• Intellectual slowness
• Insomnia 1

Diagnostic Evaluation

The initial laboratory evaluation for diagnosing Hashimoto's thyroiditis should include:

• TSH - Most sensitive initial screening test
• Free T4 - To distinguish between subclinical and overt hypothyroidism
• Thyroid antibodies - Specifically thyroid peroxidase antibodies (TPO-Ab) and thyroglobulin antibodies (TG-Ab) 3

Thyroid autoantibodies are detected in 80-85% of cases of autoimmune thyroid diseases, with TPO antibodies being one of the most common 3.

Associated Conditions

Hashimoto's thyroiditis is frequently associated with other autoimmune conditions:

• Autoimmune thyroid diseases - Most common concurrent autoimmune condition (10-23% of HT patients) 1
• Systemic lupus erythematosus - Occurs in approximately 2.8-3% of HT patients 1
• Sjögren syndrome - Observed in about 2.8-7% of HT patients 1
• Rheumatoid arthritis - Develops in approximately 2-4% of HT patients 1
• Inflammatory bowel disease - Occurs in about 2-11.4% of HT patients 1

Health Implications

Hashimoto's thyroiditis has several important health implications:

• Associated with 1.6 times higher risk of papillary thyroid cancer 2
• Associated with 60 times higher risk of thyroid lymphoma than the general population 2
• TPOAbs presence is associated with 2-4 fold increased risk of recurrent miscarriages and preterm birth in pregnant women 2
• May affect quality of life even in patients with normal thyroid function 4
• Can cause decreased left ventricular performance, gut disorders, fibromyalgia, and reproductive health issues 4

Treatment Approach

The standard treatment for hypothyroidism resulting from Hashimoto's thyroiditis is:

• Levothyroxine (LT4) - Oral T4 monotherapy at doses ranging from 1.4 to 1.8 mcg/kg/day based on the degree of preserved thyroid functionality and lean body mass 2, 1
• Monitoring - TSH and free T4 should be monitored every 6-12 months 3

For patients in different clinical phases:

• Hashitoxicosis - Symptom control usually with β-blockers
• Euthyroidism - Periodic TSH measurements to assess for progression to hypothyroidism
• Hypothyroidism - Thyroid hormone replacement therapy 2

Emerging Treatment Considerations

Some emerging treatment considerations include:

• Thyroidectomy in selected cases
• Selenium administration
• Prophylactic levothyroxine supplementation
• Lifestyle and dietary interventions 4, 5

A recent pilot study showed that a multi-disciplinary diet and lifestyle intervention using the Autoimmune Protocol diet significantly improved health-related quality of life and decreased clinical symptom burden in women with Hashimoto's thyroiditis 5.

Key Monitoring Considerations

• If initial TSH is abnormal, repeat testing should be performed within 3-6 months to confirm the diagnosis
• Multiple TSH measurements over time provide more reliable diagnostic information than a single test
• For patients on treatment, monitoring every 2-4 weeks until stable, then every 3-6 months once stable 3

Hashimoto's thyroiditis is a complex autoimmune condition that requires careful diagnosis and management to prevent complications and improve quality of life.