Points to Ponder for NEET-PG, FMGE & NEXT
- Hashimoto’s thyroiditis is the leading cause of hypothyroidism in iodine-sufficient areas.
- Autoimmune destruction of the thyroid gland by T-cells and B-cells leads to progressive hypothyroidism.
- Women are more commonly affected, with peak prevalence between 45-65 years.
- Clinical features include painless goiter and gradual onset of hypothyroid symptoms.
- Diagnosis is based on clinical features, thyroid function tests, and elevated anti-thyroid antibodies.
- Treatment involves lifelong levothyroxine replacement therapy with regular TSH monitoring.
Definition: Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis, is the most common cause of hypothyroidism in iodine-sufficient areas. It is an autoimmune disorder that affects the thyroid gland.
Pathogenesis:
- Autoimmune destruction: Lymphocytes infiltrate the thyroid gland, leading to chronic inflammation and progressive destruction of thyroid tissue.
- T-cell mediated attack: T-cells target thyroid antigens.
- B-cell activation: B-cells produce antibodies against thyroid peroxidase (TPO) and thyroglobulin.
- Genetic predisposition: Association with HLA-DR5 haplotype.
Antibodies:
- Anti-TPO (anti-thyroid peroxidase antibodies): Most common and sensitive marker.
- Anti-thyroglobulin antibodies: Can also be elevated.
Histology:
- Massive infiltration of lymphocytes with formation of germinal centers.
- Presence of Hurthle cells (enlarged, eosinophilic follicular cells).
Clinical Features:
- Predominantly affects women: More common in females, with a peak prevalence between 45-65 years old.
- Thyroid enlargement (goiter): The thyroid gland may be enlarged but is usually painless and firm.
- Hypothyroidism symptoms: Develop gradually due to progressive loss of thyroid function. Symptoms can include fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, and muscle weakness.
Complications:
- Increased risk of non-Hodgkin lymphoma: Particularly B-cell lymphomas.
- Autoimmune overlap syndromes: Increased risk of developing other autoimmune diseases, including:
- Endocrine: Type 1 diabetes, autoimmune adrenalitis.
- Non-endocrine: Systemic lupus erythematosus, myasthenia gravis, Sjögren syndrome.
Diagnosis:
- Clinical features: As mentioned above.
- Thyroid function tests: Low serum free thyroxine (FT4) and elevated thyroid-stimulating hormone (TSH) are diagnostic of hypothyroidism.
- Thyroid autoantibodies: Elevated levels of anti-TPO and/or anti-thyroglobulin antibodies support the diagnosis of Hashimoto’s thyroiditis.
- Imaging: Thyroid ultrasound may show a characteristic heterogeneous, hypoechoic pattern, but is not diagnostic and may be normal.
Treatment:
- Thyroid hormone replacement therapy: Levothyroxine is the mainstay of treatment. It replaces the missing thyroid hormone and improves symptoms.
- Monitoring: Regular monitoring of TSH levels is necessary to adjust the levothyroxine dose as needed.
