Hashimoto’s Thyroiditis

Definition

Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis, is an autoimmune disorder in which the immune system attacks the thyroid gland, leading to chronic inflammation and often resulting in hypothyroidism.

Aetiology

The exact cause of Hashimoto’s thyroiditis is not fully understood, but it is believed to involve a combination of genetic and environmental factors:

Genetic predisposition
Environmental triggers (e.g., infection, stress)
Excessive iodine intake
Radiation exposure

Pathophysiology

Hashimoto’s thyroiditis is characterised by an autoimmune response against thyroid antigens, leading to lymphocytic infiltration and destruction of thyroid tissue:

Autoantibodies: Thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb) are commonly present.
Inflammation: Chronic inflammation leads to fibrosis and atrophy of the thyroid gland.
Hypothyroidism: Progressive destruction of thyroid tissue results in decreased production of thyroid hormones (T3 and T4).

Risk Factors

Female gender (more common in women)
Age (most common in middle-aged adults)
Family history of thyroid or autoimmune diseases
Other autoimmune disorders (e.g., type 1 diabetes, rheumatoid arthritis)
Excessive iodine intake
Radiation exposure

Signs and Symptoms

Hashimoto’s thyroiditis can present with a variety of symptoms, often related to hypothyroidism:

Fatigue
Weight gain
Cold intolerance
Constipation
Dry skin and hair
Muscle weakness
Depression
Goitre (enlarged thyroid)
Irregular menstrual cycles

Investigations

Clinical history and physical examination
Thyroid function tests: TSH (elevated in hypothyroidism), free T4 (low), and free T3 (may be low or normal)
Thyroid antibodies: TPOAb and TgAb to confirm autoimmune thyroiditis
Ultrasound of the thyroid: To assess the size, texture, and presence of nodules or goitre
Fine-needle aspiration biopsy (FNAB): If a thyroid nodule is present, to rule out malignancy

Management

Primary Care Management

Thyroid hormone replacement therapy: Levothyroxine to normalise thyroid hormone levels and alleviate symptoms of hypothyroidism
Monitoring: Regular follow-up with thyroid function tests to adjust medication dosage as needed
Education: Informing patients about the chronic nature of the disease, the importance of medication adherence, and recognising symptoms of hypothyroidism and hyperthyroidism
Referral: To an endocrinologist if there are complications, difficulty managing thyroid levels, or suspicion of thyroid malignancy

Specialist Management

Evaluation and management of complications: Such as cardiovascular issues, myxoedema coma, or other autoimmune disorders
Thyroidectomy: Rarely indicated, but may be considered in cases of large goitre causing compressive symptoms or if malignancy is suspected

Example Management for Hashimoto’s Thyroiditis

A patient diagnosed with Hashimoto’s thyroiditis presenting with symptoms of hypothyroidism should be started on levothyroxine. The initial dose is typically based on the patient's weight and severity of hypothyroidism. Regular follow-up appointments are necessary to monitor thyroid function tests and adjust the levothyroxine dose to maintain TSH within the target range. The patient should be educated on the importance of taking levothyroxine on an empty stomach and avoiding certain foods and medications that can interfere with its absorption. The patient should also be informed about the chronic nature of the disease and the need for lifelong medication adherence.

References

NICE. (2024). Thyroid Disease: Assessment and Management. Retrieved from NICE
NHS. (2023). Hashimoto's Thyroiditis. Retrieved from NHS
British Thyroid Foundation. (2022). Hashimoto’s Thyroiditis. Retrieved from British Thyroid Foundation
American Thyroid Association (ATA). (2021). Guidelines for the Management of Thyroid Disease. Retrieved from ATA