Hashimoto’s thyroiditis is characterized by destructive lymphoid infiltration of the thyroid gland. It is the most frequent cause of hypothyroidism.
It is more common in women than men with a ratio of 7:1 and is more common between 30 and 50 years of age.
There’s a risk of developing thyroid lymphoma, but this is rare. There is also an association and increased risk of diabetes type 1, Grave’s disease, SLE, etc.
Etiology;
- The cause is unknown, but genetic and environmental factors play a role
- Association with DR5 and HLA-DR3 have been documented
Pathophysiology;
- T cells and humoral responses are activated. The activated B cells produce antibodies against thyroid peroxidase and thyroglobulin, thus causing thyroid tissue destruction.
Clinical features;
- Small or moderately sized goitre that is firm or rubbery in consistency
- hypothyroid symptoms- cold intolerance, weight gain, constipation, etc
- Transient thyrotoxicosis ( Hashitoxicosis) may occur. This is due to transient rupture of the follicular cells, releasing thyroid hormones. Patients present with symptoms of thyrotoxicosis in this phase
- Hashimoto encephalopathy- presents with cognitive impairment, ataxia, myoclonus, and epileptic seizures. It is caused by the autoantibodies present in Hashimoto’s thyroiditis
Investigations;
1. TFTs-
- 25% are hypothyroid at the presentation- low T3 and T4 with a high TSH
- The rest- normal TRY and TSH may be normal or high.
2. Serology-
- antithyroid peroxidase antibodies are present in >90% of patients
- Antinuclear factor( ANF) may be present in those <20 years of age
3. Ultrasound- may show thyroid gland enlargement or atrophy
4. Fine needle aspiration and cytology- to rule out malignancy
5. Radio iodine uptake- there may be decreased or increased uptake
6. Histology- diffuse lymphocytic infiltrates with Hurthle cells and fibrotic tissue
Management
- Levothyroxine for hypothyroidism and also to shrink the goitre
- Start with a low-acting dose because of the cardiotoxic side effects
- Lifelong monitoring of thyroid parameters
Differential diagnosis
- Riedel’s thyroiditis
- Grave’s disease
- Subacute thyroiditis
