There are many causes of inflammation of the thyroid gland (thyroiditis), the most common of which is Hashimoto's chronic thyroiditis, an inflammatory disorder caused by abnormal blood antibodies and lymphocytes which attack thyroid cells. This autoimmune disorder ultimately completely destroys the thyroid cells (causing hypothyroidism). In many cases, however, sufficient thyroid gland remains in order to prevent hypothyroidism.
The disorder usually affects young, middle-aged, or older women. The patients often have no symptoms but experience slight pressure on their thyroid gland and a certain degree of tiredness. In the early stage of the disease they have a firm, slightly irregular and occasionally slightly painful (10 per cent of cases) goitre.
The diagnosis can be confirmed by finding high levels of antibodies in the blood, which attack thyroid proteins. The diagnosis can be confirmed by biopsy. The surgeon inserts a needle into the thyroid to remove cells, which are examined by a pathologist on a slide. The presence of a great man lymphocytes indicates inflammation of the thyroid gland.
Even if the gland is functioning normally at the time, this disease is treated by administering thyroid hormones (thyroxine) from diagnosis
Source: The Canadian Thyroid Foundation