Thyroiditis refers to a group of disorders characterized by inflammation of the thyroid gland. This inflammation may lead to dysfunction of the gland, manifesting as hyperthyroidism, hypothyroidism, or even a biphasic pattern where hyperthyroidism precedes hypothyroidism. 

Thyroiditis is classified into different types based on its cause, symptoms, and course of illness. The most common types of thyroiditis include:

1-Hashimoto's thyroiditis: This is an autoimmune disorder that causes the body to attack the thyroid gland. It is the most common cause of hypothyroidism, which is an underactive thyroid.

2-Subacute thyroiditis: This is caused by a viral infection of the thyroid gland. It is characterized by a painful, swollen thyroid gland and a transient period of hyperthyroidism, which is an overactive thyroid.

3-Postpartum thyroiditis: This occurs in about 5% of women after childbirth. It is characterized by a transient period of hyperthyroidism followed by hypothyroidism.

4-Silent thyroiditis: This is a type of Hashimoto's thyroiditis that does not cause any symptoms. It is often diagnosed incidentally when a blood test reveals low thyroid hormone levels.

5-Drug-induced thyroiditis: This can be caused by certain medications, such as amiodarone and lithium. It is characterized by a transient period of hyperthyroidism followed by hypothyroidism.

In addition to these common types, there are also a few rarer types of thyroiditis, including:

6-Acute thyroiditis: This is a rare type of thyroiditis that is caused by a bacterial infection. It is characterized by a sudden onset of fever, pain, and swelling in the thyroid gland.

7-Riedel's thyroiditis: This is a rare type of thyroiditis that is characterized by the thickening and scarring of the thyroid gland. It can cause hypothyroidism and difficulty swallowing.

8-Thyroiditis caused by radiation therapy: This type of thyroiditis can occur after radiation therapy for cancer of the head or neck. It is characterized by hypothyroidism and pain in the thyroid gland.

The treatment for thyroiditis depends on the type of thyroiditis and the severity of the symptoms. In most cases, thyroiditis is treated with medication, such as thyroid hormone replacement therapy or anti-inflammatory drugs. In some cases, surgery may be necessary to remove the thyroid gland.

The prognosis for thyroiditis is generally good. With treatment, most people with thyroiditis can return to their normal activities and live a normal, healthy life.