OVERVIEW
The thyroid gland is a butterfly-shaped gland (weighing about 15-20 grams) situated in the front of the lower part of neck and secretes thyroid hormones that are key regulators of metabolism
Thyroiditis, or thyroid gland inflammation can cause over- and under-production of thyroid hormones and can disturb the normal metabolism
Thyroiditis is not an infection of the thyroid gland (only rare cases)
There are several causes for thyroiditis and treatments depends on the cause

PATHOPHYSIOLOGY OF THYROIDITIS
The thyroid gland can be attacked by several agents. These cause injury inflammation and injury to the thyroid cells resulting in thyroiditis

CAUSES OF THYROIDITIS
• Autoimmune thyroiditis (most common)
• Drugs
• Radiotherapy
• Microbial infection (bacteria and virus)
• Genetic predisposition

TYPES OF THYROIDITIS
1. Hashimoto’s thyroiditis
It is an autoimmune condition caused by anti-thyroid antibodies, and is the most common form of thyroiditis. Women are more affected than men. Hashimoto’s thyroiditis typically causes hypothyroidism and is treated by replacing thyroid hormone
2. Silent thyroiditis or painless thyroiditis
This is also caused by anti-thyroid antibodies and affects women more. It is the second most common type after Hashimoto’s thyroiditis.
3. Post-partum thyroiditis
This condition is caused by formation of anti-thyroid antibodies in some women following childbirth
4. Radiation-induced thyroiditis
Condition caused by external radiation to treat certain cancers, or radioactive iodine to treat hyperthyroidism
5. Subacute thyroiditis or de Quervain’s thyroiditis
A painful condition believed to be caused by a viral attack
6. Acute thyroiditis or suppurative thyroiditis
Rare type of thyroiditis caused by an infectious organism or bacterium
7. Drug-induced thyroiditis
Thyroiditis caused by the use of drugs such as lithium, amiodarone, interferons and cytokines. It only occurs in a small proportion of patients using the drug.

PHASES OF THYROIDITIS
Thyrotoxic phase – In the thyrotoxic phase, the gland is inflamed and secretes excess hormones.
Hypothyroid phase – Following the excessive secretion thyroid hormones for a few weeks or months, there is a lack of thyroid hormones or stage of hypothyroidism.
Euthyroid phase – During the euthyroid phase, the thyroid hormone levels are normal. This phase may follow the thyrotoxic phase before going to the hypothyroid phase, or may follow the hypothyroid phase once the thyroid gland has recovered normal function

SYMPTOMS OF THYROIDITIS
Symptoms depend on the stage of thyroiditis

DIAGNOSIS OF THYROIDITIS
• Thyroid function tests
These estimate amounts of hormones (thyroid-stimulating hormone or TSH, T3, and T4) in the blood. TSH is secreted by the pituitary or the master gland and stimulates the thyroid gland to produce T4 and T3, which are the thyroid hormones.
• Thyroid antibody tests
Thyroid antibodies are measured namely antithyroid (microsomal) antibodies (TPO) or thyroid receptor stimulating antibodies (TRAb).
• Erythrocyte sedimentation rate (ESR)
This test indicates presence of inflammation by measuring how fast red blood cells drawn into a graduated long tube placed vertically on a stand fall. It is expressed in mm/hr. The ESR is elevated in sub-acute thyroiditis.
• Ultrasound (USG)
Ultrasound of the thyroid is done frequently to evaluate the anatomy of the thyroid gland. It can demonstrate a nodule or tumor in the thyroid gland, blood flow pattern and echo texture (intensity/density) of the gland.
• Radioactive iodine uptake (RAIU)
This test measures the amount of radioactive iodine absorbed by the thyroid gland. The amount is always low in the thyrotoxic phase of thyroiditis.

TREATMENT OF THYROIDITIS
Treatment depends on the type, symptoms, and phase of thyroiditis.
1. Thyrotoxic phase
This phase is short lived and eventually recovers or goes to the euthyroid phase, or hypothyroid phase. During the thyrotoxic phase, management is symptomatic and anti-thyroid agents are rarely if ever required.
2. Anxiety/palpitations/tremors/increased sweating/heat intolerance
Treated with beta blockers.
3. Thyroidal pain
Treated with anti-inflammatory medications such as aspirin or ibuprofen. If the pain is severe, steroid therapy may be necessary
4. Suppurative thyroiditis
Treating the infection with antibiotics is important in suppurative thyroiditis
5. Drug-induced thyroiditis
Stopping the offending drug
6. Hypothyroid phase
Thyroid hormone replacement therapy to treat hypothyroidism for about 6 to 12 months. Hashimoto’s thyroiditis typically results in permanent hypothyroidism needing prolonged treatment

PROGNOSIS
• In Hashimoto’s thyroiditis, the resulting hypothyroidism is generally permanent.
• In subacute thyroiditis symptoms may last for 1 to 3 months, but complete recovery of thyroid function is the norm and can take up to 12 to 18 months. These patients may rarely go on to develop permanent hypothyroidism.
• Recovery of normal thyroid functions for post-partum, silent or painless thyroiditis takes around 12 to 18 months. Approximately 20% of these patients develop permanent hypothyroidism.