Subacute Lymphocytic Thyroiditis / Painless Thyroiditis

What You Need to Know About Painless Silent Thyroiditis

Doctor Examining Patient's Thyroid
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The term thyroiditis refers generally to any disorder that involves inflammation of your thyroid gland. Thyroiditis is typically divided into two broad categories (painless and painful) that characterize the degree of pain they cause to patients.

Painless thyroiditis is also frequently referred by a number of other names, including silent thyroiditis, subacute lymphocytic thyroiditis, atypical subacute thyroiditis, transient thyrotoxicosis with low RAIU, hyperthyroiditis, and lymphocytic thyroiditis with spontaneously resolving hyperthyroidism.


While some forms of thyroiditis are accompanied by thyroid enlargement, known as goiter, in painless thyroiditis, the thyroid gland usually does not become enlarged.


If you have painless thyroiditis, you are considered to have a form of autoimmune thyroid disease, like Hashimoto's thyroiditis, except that in many cases, it will resolve over time and your thyroid will return to normal function. The causes of most autoimmune diseases are not known or well understood.  

Certain medications are also known to cause painless thyroiditis. If you are taking the following medications, it's important to be aware that they may cause painless thyroiditis in some patients:

  • Interferon-alfa: a medication used to treat some viral infections and cancers
  • Interleukin-2: a medication used as a cancer treatment
  • Amiodarone: a medication used to treat an irregular heartbeat
  • Lithium: a mood-stabilizing drug used to treat bipolar disorder


    In some cases, painless thyroiditis will have no symptoms. But the condition may also be accompanied by symptoms, especially hyperthyroidism symptoms in the early stages. These symptoms may last for up to three months, and may include: 

    • Fatigue
    • Weakness in muscles
    • Frequent bowel movements, loose bowels, diarrhea
    • Intolerance to heat, increased sweating
    • An increased appetite
    • Increased food intake without weight gain, or unexpected weight loss
    • Irregular menstrual periods
    • Feeling nervous, anxious, restless, or irritable 
    • Heart palpitations
    • Insomnia 

    Later, your symptoms may shift to those of an underactive thyroid (hypothyroidism), and may include including fatigue, weight gain, hair loss, depression, and cold intolerance.

    Some people only notice the hypothyroid symptoms and do not have symptoms of hyperthyroidism.


    It's estimated that painless thyroiditis may be the cause for as much as 10 to 20 percent of cases of hyperthyroidism (an overactive thyroid) and 10 percent of hypothyroidism.

    Painless thyroiditis frequently resolves itself within two to four months, but in some cases, it can last as long as a year. It's estimated that over time as many as 95 percent of patients will return to normal thyroid function. 

    It's important for your doctor to make an accurate diagnosis because in most cases, specific thyroid treatment, such as antithyroid drugs or thyroid hormone replacement therapy, is not necessary. 


    Diagnosis of painless thyroiditis typically involves a thorough clinical examination, including a manual examination of your thyroid gland, TSH, Free T4 and Free T3 tests, and radioactive iodine uptake (RAI-U) in some cases.

    RAI-U shows decreased uptake in painless thyroiditis. Less commonly, a thyroid biopsy -- known as a fine needle aspiration (FNA) biopsy -- may be performed to make a definitive diagnosis.


    Painless thyroiditis is frequently a short-term, transient condition, and typically doesn't cause severe thyroid dysfunction. When treatment is needed, it is usually for the symptoms. So, for example, if you are experiencing a high heart rate or palpitations during a hyperthyroid phase of painless thyroiditis, you might be prescribed a short course of a beta-blocking drug. Or if you have a prolonged hypothyroid phase, you may be prescribed a course of thyroid hormone replacement medication until the thyroid gradually returns to normal functioning.


    Around 20 percent of patients do develop chronic hypothyroidism or recurrent thyroiditis, however, so it is important to have periodic follow-up with your physician. 


    View Article Sources
    • Burman, Kenneth. Ross, Douglas. Martin, Kathryn. "Overview of thyroiditis." UpToDate.
    • Schwartz F, Bergmann N, Zerahn B, Faber J. Incidence rate of symptomatic painless thyroiditis presenting with thyrotoxicosis in Denmark as evaluated by consecutive thyroid scintigraphies. Scand J Clin Lab Invest 2013; 73:240.