Chapter 6 - Thyroiditis
 
  1. Hashimoto's Thyroiditis
  2. De Quervain's Thyroiditis
  3. Silent Thyroiditis
Thyroiditis is an inflammation (not an infection) of the thyroid gland. Several types of thyroiditis exist and the treatment is different for each.

A. Hashimoto's Thyroiditis

Hashimoto's Thyroiditis (also called autoimmune or chronic lymphocyctic thyroiditis) is the most common type of thyroiditis. It is named after the Japanese physician, Hakaru Hashimoto, that first described it in 1912. The thyroid gland is always enlarged, although only one side may be enlarged enough to feel. The thyroid tissue becomes inefficient in converting iodine into thyroid hormone and "compensates" by enlarging. The radioactive iodine uptake may be paradoxically high while the patient is hypothyroid because the gland retains the ability to take-up or "trap" iodine even after it has lost its ability to produce thyroid hormone. As the disease progresses, the TSH increases, the T4 falls and the patient becomes hypothyroid. The sequence of events can occur over a relatively short span of a few weeks or may take several years.

Treatment is to start thyroid hormone replacement. This prevents or corrects the hypothyroidism and it also generally keeps the gland from getting larger. In most cases the thyroid gland will decrease in size once thyroid hormone replacement is started. Thyroid antibodies are present in 95% of patients with Hashimoto's Thyroiditis and serve as a useful "marker" in identifying the disease without thyroid biopsy or surgery. These antibodies may remain for years after the disease has been adequately treated and the patient is on thyroid hormone replacement.

B. De Quervain's Thyroiditis

De Quervain's Thyroiditis (also called subacute or granulomatous thyroiditis) was first described in 1904 and is much less common than Hashimoto's Thyroiditis. The thyroid gland generally swells rapidly and is very painful and tender. The gland discharges thyroid hormone into the blood and the patients become hyperthyroid; however the gland quits taking up iodine (radioactive iodine uptake is very low) and the hyperthyroidism generally resolves over the next several weeks. The patients frequently become ill with fever and must go to bed. Thyroid antibodies are not present in the blood, but the sedimentation rate, which measures inflammation, is very high.

Although this type of thyroiditis resembles an infection, no infectious agent has ever been identified and antibiotics are of no use. Treatment is usually bed rest and aspirin to reduce inflammation. Occasionally cortisone (to reduce inflammation) and thyroid hormone (to "rest" the thyroid gland) may be used in prolonged cases. Nearly all patients recover and the thyroid gland returns to normal after several weeks or months. A few patients become hypothyroid and need to stay on thyroid hormone replacement indefinitely. Recurrences are uncommon.

C. Silent Thyroiditis

Silent Thyroiditis is a third type of thyroiditis. It was not recognized until the 1970's although it probably existed and was treated as Graves' Disease before that. This type of thyroiditis resembles in part Hashimoto's Thyroiditis and in part De Quervain's Thyroiditis. The blood thyroid test are high and the radioactive iodine uptake is low (like De Quervain's Thyroiditis), but there is no pain and needle biopsy resembles Hashimoto's Thyroiditis. The majority of patients have been young women following pregnancy. The disease usually needs no treatment and 80% of patients show complete recovery and return of the thyroid gland to normal after three months.

Symptoms are similar to Graves' Disease except milder. The thyroid gland is only slightly enlarged and exophthalmos does not occur. Treatment is usually bed rest with Inderal to control palpitations. Radioactive iodine, surgery, or antithyroid medication is never needed. A few patients have become permanently hypothyroid and needed to be placed on thyroid hormone.

An outbreak of what appeared to be silent thyroiditis occurred in a small town in South Dakota in 1985 with 121 cases in a six month period. This epidemic turned out not to be silent thyroiditis, but hyperthyroidism caused by hamburger meat in which the thyroid gland had been ground up with other meat. The thyroid scan failed to show a functioning thyroid gland in these patients indicating the high level of thyroid hormone in the blood was from some other source.