
Hashimotos Thyroiditis
Endocrine system
Hashimoto’s Thyroiditis
Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis, is an autoimmune disorder in which the immune system attacks the thyroid gland. It is the most common cause of hypothyroidism in iodine-sufficient regions and predominantly affects middle-aged women.
Pathophysiology:
• The immune system produces antibodies against thyroid antigens, including:
o Thyroid peroxidase (TPO) antibodies.
o Thyroglobulin (Tg) antibodies.
• This leads to chronic inflammation and destruction of thyroid tissue, resulting in reduced thyroid hormone production over time.
Causes and Risk Factors:
• Genetics: Family history of autoimmune diseases increases risk.
• Gender: More common in women (10:1 female-to-male ratio).
• Age: Typically affects people between 30 and 50 years.
• Environmental Factors:
o Iodine excess or deficiency.
o Certain medications (e.g., amiodarone, lithium).
o Radiation exposure.
Clinical Features:
• Early Stage (Euthyroid or Subclinical Hypothyroidism):
o Asymptomatic or mild symptoms.
• Symptoms of Hypothyroidism (Later Stage):
o Fatigue.
o Weight gain.
o Cold intolerance.
o Constipation.
o Dry skin and hair thinning.
o Depression and cognitive slowing (brain fog).
o Hoarseness.
o Menstrual irregularities.
o Puffy face and periorbital edema.
• Goitre (Enlarged Thyroid):
o Diffuse, firm, and rubbery thyroid enlargement.
o May cause a feeling of fullness in the neck but usually not compressive symptoms.
Gross Appearance:
• Size and Shape:
o Enlarged, symmetric thyroid gland.
• Surface:
o Firm and lobulated.
• Color and Texture:
o Pale, greyish-white cut surface with a nodular appearance.
Microscopic (Histological) Features:
1. Lymphocytic Infiltration:
o Dense infiltration of lymphocytes, forming germinal centers.
2. Follicular Atrophy:
o Thyroid follicles are reduced in size and may be destroyed.
3. Hurthle Cell Change (Oncocytic Metaplasia):
o Follicular cells transform into large, eosinophilic cells with granular cytoplasm.
4. Fibrosis:
o Variable degrees of fibrosis but typically confined within the thyroid capsule.
Diagnosis:
• Thyroid Function Tests:
o Early: Normal T3 and T4 with elevated TSH (subclinical hypothyroidism).
o Later: Low T3 and T4 with elevated TSH (overt hypothyroidism).
• Autoantibodies:
o Positive anti-TPO antibodies (most sensitive marker).
o Positive anti-thyroglobulin antibodies.
• Ultrasound:
o Heterogeneous, hypoechoic thyroid with a "pseudonodular" appearance.
o Diffuse enlargement and possible increased vascularity.
• Fine-Needle Aspiration (FNA):
o May be done if nodules are present to rule out malignancy.
Management:
• Thyroid Hormone Replacement:
o Levothyroxine (T4) is the treatment of choice for hypothyroidism.
o Dose adjustments are based on TSH levels and clinical response.
• Monitoring:
o Regular follow-up with thyroid function tests every 6-12 months or after dosage changes.
• Surgery:
o Rarely needed but may be considered for large goitres causing compressive symptoms or for cosmetic reasons.
Complications:
• Myxedema: Severe hypothyroidism leading to life-threatening symptoms like hypothermia, bradycardia, and altered mental status.
• Increased Risk of Thyroid Lymphoma: Although rare, Hashimoto’s thyroiditis is associated with an increased risk of developing primary thyroid lymphoma.
Prognosis:
• Good with treatment: Most patients achieve normal thyroid function with levothyroxine therapy.
o Lifelong condition: Requires long-term monitoring and treatment.