What are the clinical symptoms of thyroiditis?
There are no symptoms unique to thyroiditis. If the thyroiditis causes slow and chronic thyroid cell damage and destruction, leading to a fall in thyroid hormone levels in the blood, the symptoms would be those of hypothyroidism (see Hypothyroidism brochure). Typical hypothyroid symptoms include fatigue, weight gain, constipation, dry skin, depression and poor exercise tolerance. This would be the case in patients with Hashimoto’s thyroiditis. If the thyroiditis causes rapid thyroid cell damage and destruction, the thyroid hormone that is stored in the gland leaks out, increasing thyroid hormone levels in the blood, and produces symptoms of thyrotoxicosis, which are similar to hyperthyroidism (see Hyperthyroidism brochure). These symptoms often include anxiety, insomnia, palpitations (fast heart rate), fatigue, weight loss, and irritability. This is seen in patients with the toxic phase of subacute, painless and post-partum thyroiditis. The symptoms of thyrotoxicosis and hyperthyroidism are identical, as elevated levels of thyroid hormone in the blood cause both conditions. Thyrotoxicosis is the term used with thyroiditis since the gland is not overactive. In subacute, painless and post-partum thyroiditis, the thyroid gland often becomes depleted of thyroid hormone as the course of inflammation continues, leading to a fall in thyroid hormone levels in the blood and symptoms of hypothyroidism. Pain in the thyroid can be seen in patients with subacute thyroiditis

CAUSES

What causes thyroiditis?
Thyroiditis is caused by an attack on the thyroid, causing inflammation and damage to the thyroid cells. Antibodies that attack the thyroid cause most types of thyroiditis. As such, thyroiditis is often an autoimmune disease, like juvenile diabetes and rheumatoid arthritis. No one knows why certain people make thyroid antibodies, although this tends to run in families. Thyroiditis can also be caused by an infection, such as a virus or bacteria, which work in the same way as the antibodies to cause inflammation in the gland. Finally, drugs such as interferon and amiodarone, can also damage thyroid cells and cause thyroiditis.

What is the clinical course of thyroiditis?
The course of thyroiditis depends on the type of thyroiditis.

Hashimoto’s thyroiditis – Patients usually present with hypothyroidism, which is usually permanent.

Painless and post-partum thyroiditis – These disorders are similar and follow the same general clinical course of thyrotoxicosis followed by hypothyroidism. The only real difference between them is that post-partum thyroiditis occurs after the delivery of a baby while painless thyroiditis occurs in men and in women not related to a pregnancy. Not all patients demonstrate evidence of going through both phases; approximately 1/3 of patients will manifest both phases, while 1/3 of patients will have only a thyrotoxic or hypothyroid phase. The thyrotoxic phase lasts for 1-3 months and is associated with symptoms including anxiety, insomnia, palpitations (fast heart rate), fatigue, weight loss, and irritability. The hypothyroid phase typically occurs 1-3 months after the thyrotoxic phase and may last up to 9 – 12 months. Typical symptoms include fatigue, weight gain, constipation, dry skin, depression and poor exercise tolerance. Most patients (~80%) will have return of their thyroid function to normal within 12-18 months of the onset of symptoms.

Subacute thyroiditis – Subacute thyroiditis follows the same clinical course as painless and post-partum thyroiditis, with the exception of the symptoms of thyroidal pain. The thyroidal pain in patients with subacute thyroiditis usually follows the same time-frame of the thyrotoxic phase (1-3 months). However, not all patients with thyroidal pain necessarily have thyrotoxicosis. As noted with painless and post-partum thyroiditis, resolution of all thyroidal abnormalities after 12-18 months is seen in most patients (~95%). Recurrence of subacute thyroiditis is rare.

Drug-induced and radiation thyroiditis – Both thyrotoxicosis and hypothyroidism may be seen in these disorders. The thyrotoxicosis is usually short-lived. Drug-induced hypothyroidism often resolves with the cessation of the drug, while the hypothyroidism related to radiation thyroiditis is usually permanent.

Acute/Infectious thyroiditis – Symptoms range from thyroidal pain, systemic illness, painless enlargement of the thyroid and hypothyroidism. The symptoms usually resolve once the infection resolves.

What are the Types of Thyroiditis? There are many types of thyroiditis, which are summarized in the table below: