Hashimoto’s Thyroiditis

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Hashimoto’s thyroiditis is a chronic autoimmune thyroid disorder characterised by lymphocytic infiltration, progressive thyroid destruction, and eventual hypothyroidism.

Aetiology

  • Autoimmune-mediated destruction: caused by T-cell mediated cytotoxicity and antibody production against thyroid peroxidase (TPO) and thyroglobulin.
  • Genetic predisposition: associated with HLA-DR3, HLA-DR4, and HLA-DR5.
  • Environmental factors: iodine excess, infections, and stress may trigger autoimmunity.

Pathophysiology

  • Thyroid tissue is infiltrated by lymphocytes, leading to follicular destruction.
  • Progressive fibrosis results in gland dysfunction and hypothyroidism.
  • Antibodies against TPO and thyroglobulin interfere with thyroid hormone synthesis.

Risk Factors

  • Female sex (7:1 female-to-male ratio).
  • Family history of autoimmune thyroid disease.
  • Other autoimmune diseases (e.g., type 1 diabetes, rheumatoid arthritis, coeliac disease).
  • High iodine intake.
  • Radiation exposure.

Signs and Symptoms

  • Early stage: may be asymptomatic or present with transient hyperthyroid symptoms (Hashitoxicosis).
  • Hypothyroid symptoms:
    • Fatigue, weight gain, cold intolerance.
    • Dry skin, brittle hair, constipation.
    • Depression, memory impairment.
  • Neck examination:
    • Goitre (diffuse, firm, non-tender enlargement of the thyroid gland).
    • Late-stage fibrosis may lead to gland atrophy.

Investigations

  • Thyroid function tests: high TSH, low free T4 in overt hypothyroidism.
  • Thyroid autoantibodies: positive anti-TPO and anti-thyroglobulin antibodies.
  • Ultrasound: heterogeneous, hypoechoic thyroid gland.
  • Fine-needle aspiration (FNA): if malignancy is suspected.

Management

1. Hormone Replacement Therapy:

  • Levothyroxine: first-line treatment, titrated based on TSH levels.
  • Monitor TSH every 6–8 weeks initially, then annually once stable.

2. Symptomatic Management:

  • Supportive treatment for fatigue, weight gain, and constipation.

3. Referral:

  • Endocrinology: if diagnosis is unclear, unstable TSH levels, or suspected malignancy.
  • Surgery: if compressive symptoms (e.g., dysphagia, airway obstruction) or suspicion of malignancy.
EndocrinologymypanotesHashimoto’s Thyroiditis