Hashimoto's disease is the most common cause of thyroiditis, but there are other conditions that can cause your thyroid gland to become inflamed. Some of these are fairly common, and others are really rather rare. Still, if your thyroid gland is inflamed and blood tests have ruled out Hashimoto's, it's quite possible that you have another form of thyroiditis.

Subacute Thyroiditis

You arrive at the doctor's office complaining of a sore throat and flulike symptoms. Moments later, after touching your neck, your doctor says that the real culprit may be a thyroid problem. Chances are, you have subacute thyroiditis, which is sometimes called deQuervain 's thyroiditis, named for the Swiss surgeon who first described the condition in 1904.

Subacute thyroiditis usually occurs after a bout of the flu or another upper respiratory infection. It has also been linked to other viral diseases, including mumps and Coxsackie virus. Usually, patients will notice pain in the lower neck and rapid enlargement of the thyroid gland. Some people may develop a fever, hoarseness, and difficulty swallowing. In some cases, the condition is mild and barely noticeable and simply goes away on its own.

For other people, however, the condition may be more progressive. During the early stages, as the thyroid gland releases excess hormone into the bloodstream, subacute thyroiditis may cause symptoms of hyperthyroidism, such as nervousness, anxiety, a rapid heartbeat, and an intolerance for heat. After a while, these symptoms will evolve into those of hypothyroidism, with fatigue, forgetfulness, dry skin, and intolerance for the cold becoming more prominent.

Diagnosing subacute thyroiditis can be tricky and is often a process of elimination. The most obvious sign is a painful neck. But other indicators in the blood, such as the erythrocyte sedimentation rate, may also reveal a great deal of inflammation. If necessary, an RAI uptake test might be done. Results that are low would reveal very little uptake of iodine in the inflamed thyroid.

Treatment for subacute thyroiditis usually involves bed rest and aspirin to reduce the inflammation. In more severe cases, cortisone may be given to tame the inflammation, and thyroid hormone replacement may be needed to restore the missing hormones. But the condition usually resolves itself after several weeks or months, and the thyroid gland returns to normal function. In rare cases, you may be placed on thyroid hormone for good if normal thyroid function does not resume.

Silent Thyroiditis

Silent thyroiditis is just that: a quiet condition that produces no obvious symptoms and causes no pain. And yet, the thyroid is inflamed. The only way to know you have it is if you develop symptoms of hyperthyroidism.

Like subacute thyroiditis, the initial inflammation sometimes causes too much thyroid hormone to leak into the bloodstream, producing symptoms of hyperthyroidism. After a while, you may notice some symptoms of hypothyroidism, as the hormone release slows and the thyroid gland remains inflamed.

The cause of silent thyroiditis is unknown, but tests have found that the thyroid gland in silent thyroiditis is filled with lymphocytes, a type of white blood cell involved in the immune system. For that reason, experts believe that silent thyroiditis is a temporary malfunction of the immune system.

Like the subacute form, silent thyroiditis usually resolves on its own with bed rest and aspirin to treat the inflammation. Usually, no other treatment is needed unless a patient becomes permanently hypothyroid, which is rare.

Postpartum Thyroiditis

Most cases of silent thyroiditis occur after a woman delivers a baby, hence the name postpartum thyroiditis. The condition typically occurs four to twelve months after delivery, and is most common in women who already have an autoimmune problem or thyroid disorder. Often, it goes undetected because the woman assumes her symptoms are part of the rigors of new motherhood.

Like silent thyroiditis, the postpartum version follows a similar course of events: inflammation of the gland leads first to symptoms of hyperthyroidism, followed by a period of hypothyroidism.

In some cases of postpartum thyroiditis, there is no treatment, just the passage of time. The condition usually resolves itself twelve to eighteen months after it starts. But if symptoms are more severe, you may be given an antithyroid drug such as propylthiouracil (PTU) or beta-blockers, which slow your heart rate, for hyperthyroidism, or thyroid hormone replacement for hypothyroidism. You will still be able to breast-feed while taking these medications.

Acute Suppurative Thyroiditis

In rare cases, bacteria can invade the thyroid gland, particularly the left lobe, and trigger inflammation. Acute suppurative thyroiditis is a bacterial infection of the thyroid that is extremely rare and tends to occur in children. The infection causes pus to form and the thyroid gland to become extremely painful. The condition also causes fever and chills as the body battles the infection.

Acute thyroiditis is treated with antibiotics. In more severe cases, you may need surgery to drain the infection. But the condition generally does not cause any long-term problems with the thyroid.

Riedel's Thyroiditis

Riedel's thyroiditis is an extremely rare condition that involves the buildup of scar tissue in and around the thyroid gland. In Riedel's, the thyroid gland becomes inflamed and attaches itself to nearby tissues such as the windpipe (trachea) or your vocal cords. The growth of fibrous tissue is painless but may make it hard to swallow. You may also notice that your voice is deeper than normal, and that you have some trouble breathing. Eventually, the thyroid gland becomes very hard and enlarged.

Usually, you will need a biopsy to determine whether it is inflammation or cancer that is causing the thyroid to harden and enlarge. Treatment depends on the extent of the disease, and may range from the use of steroids to surgery. If the condition destroys the hormone-production capability of the thyroid gland, you will need replacement hormone.