Subacute thyroiditis refers to inflammation of the thyroid gland, which has a clinical course of several weeks. Usually it is triggered by an acute upper respiratory tract infection (URI), such as a common cold.

Symptoms of Subacute Thyroiditis

Symptoms of Subacute Thyroidits occur in two phases:

Symptoms of hyperthyroidism:

Pain in the thyroid area. At times, pain also radiates to the ear.
Restlessness
Palpitations
Insomnia/anxiety
Excessive perspiration
Intolerance to heat
Excessive weight loss despite good appetite

A few (6-12) weeks later, these symptoms subside on their own and symptoms of hypothyroidism develop.

symptoms of hypothyroidism:

Fatigue, sluggishness
Weight gain
Intolerance to cold
Depressed mood

What Causes Subacute Thyroiditis?

The cause of subacute thyroiditis is an inflammation of the thyroid gland, secondary to an upper respiratory tract infection (URI), which causes structural damage to the thyroid gland. It’s like a tornado hitting a trailer park.

Normally, the thyroid gland stores a large amount of thyroid hormones to be released in small quantities over a period of time.

With the destruction of the gland caused by the tornado of subacute thyroiditis, the large quantities of the stored thyroid hormones gets released into the blood circulation. This causes the phase of hyperthyroidism.

The thyroid hormones remain in circulation for a few weeks (6-12 weeks) and so does the phase of hyperthyroidism.

After the tornado goes away, the thyroid gland starts to repair itself, but it takes a while.

During this period, there is shortage of thyroid hormones, which gives rise to the phase of hypothyroidism. This phase typically last a few weeks (6-12 weeks).

Eventually, in most cases, the thyroid gland restores back to normal, although some patients may become hypothyroid permanently.

Diagnosis of Subacute Thyroiditis

Diagnosis of subacute thyroiditis is a tricky one. Patients usually consult their family physicians, who often do not think about the possibility of subacute thyroiditis. Patients get placed on a variety of medicines to control their symptoms which do not get better and they feel quite frustrated. Usually, it takes an endocrinologist to diagnose subacute thyroiditis.

Diagnostic Tests include:

TSH, Free T4, FreeT3
Thyroid Antibody tests
Thyroid Radioiodine uptake and scan

Thyroid Radioiodine uptake and scan is the most useful tool in deciding whether hyperthyroidism is due to subacute thyroiditis or Graves’ disease. In subacute thyroiditis, radioiodine uptake is minimal. On the other hand, it is elevated in Graves’ disease.

The Thyroid Radioiodine uptake and scan should not be done if a patient is pregnant or breast-feeding.

Treatment of Subacute Thyroiditis

In the majority of cases, subacute thyroiditis is a self-limiting disease. Therefore, no specific treatment is required. However, close monitoring is essential.

Symptoms of hyperthyroidism can be managed with a Beta-Blocker such as atenolol or propranolol.

If pain in the thyroid area is intolerable, a short course of oral steroids, such as Prednisone, is quite helpful.

Symptoms of hypothyroidism may require a short course of thyroid hormone replacement with T4 and T3.

Patient education and close monitoring of the thyroid functions are the most important component of the treatment.

Excerpts from my book,”Graves’ Disease And Hyperthyroidism”