What are the other Names for this Condition? (Also known as/Synonyms)

• SLT (Subacute Lymphocytic Thyroiditis)

What is Subacute Lymphocytic Thyroiditis? (Definition/Background Information)

• Subacute Lymphocytic Thyroiditis (SLT) is a disorder of the thyroid gland that usually lasts for a short period; it generally does not cause any long-term or irreversible thyroid abnormalities. In a majority of cases, the condition is noted in women postpartum
• There are two types of Subacute Lymphocytic Thyroiditis, namely:
  • Silent lymphocytic thyroiditis or postpartum thyroiditis: It is usually noted in women who have recently given birth to a child. In this type, no tenderness or pain in the thyroid gland is observed
  • Sporadic painless thyroiditis or painless thyroiditis: It is noted in both men and women, and is not associated with delivery of a child (non postpartum)
• Subacute Lymphocytic Thyroiditis constitutes of three variable phases, which includes hyperthyroidism (increased thyroid hormone secretion), followed by hypothyroidism (decreased thyroid hormone secretion), and a return to euthyroid state (a state of normal thyroid function)
• The cause of Subacute Lymphocytic Thyroiditis is unknown. The risk factors that contribute towards its development include certain autoimmune disorders, women in postpartum stage, and a family history of thyroid disorders
• The signs and symptoms of Subacute Lymphocytic Thyroiditis depend on the clinical state of the condition. Hyperthyroidism may present with rapid weight loss, irritability, heat sensitivity, diarrhea, and irregular heartbeat. Hypothyroidism may result in weight gain, irritability, cold intolerance, constipation, slow heartbeat, sweating, and fatigue
• A diagnosis of Subacute Lymphocytic Thyroiditis is made by measuring thyroid hormone levels in blood and through an ultrasound scan of the thyroid gland. In many individuals, no treatment may be necessary, and the condition is known to resolve within a few months. The prognosis of Subacute Lymphocytic Thyroiditis is mostly excellent

Who gets Subacute Lymphocytic Thyroiditis? (Age and Sex Distribution)

• It is reported that between 29-50% of all forms of thyroiditis are Subacute Lymphocytic Thyroiditis cases
• Individuals of all ages may be affected by Subacute Lymphocytic Thyroiditis. However, the incident rate is higher among middle-aged adults
• The condition more often affects females (especially women between 30-50 years) than males
• Individuals of all racial and ethnic groups are affected

What are the Risk Factors for Subacute Lymphocytic Thyroiditis? (Predisposing Factors)

Risk factors associated with Subacute Lymphocytic Thyroiditis include:

• Female gender, especially postpartum women; between 5-10% of all postpartum women are known to develop the condition
• Women with a history of postpartum Subacute Lymphocytic Thyroiditis have a higher risk for recurrence of the condition following the next pregnancy
• Positive family history of the condition (or other forms of thyroiditis)
• Presence of autoimmune disorders or a family history of the same
• Radiation therapy
• Viral infections

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Subacute Lymphocytic Thyroiditis? (Etiology)

The exact cause of Subacute Lymphocytic Thyroiditis is not well-established.

• It is believed to develop due to an immune attack by the body against the thyroid gland (autoimmune disorder) that may be triggered by various factors
• It is reported that almost all individuals present antithyroid peroxidase antibodies (indicating some form of autoimmune thyroid disease), and between 50% to 80% of them present antimicrosomal antibodies (antibodies generated when the thyroid gland is damaged)

What are the Signs and Symptoms of Subacute Lymphocytic Thyroiditis?

Subacute Lymphocytic Thyroiditis typically begins with hyperthyroidism that may last for a short period. This is generally followed by hypothyroidism, resulting in associated symptoms, and is followed by a return to normal state (euthyroidism). However, the course of the condition may be variable; it may alternate between hyperthyroidism and hypothyroidism too.

The associated signs and symptoms of hyperthyroidism may include:

• Sleeping difficulties including insomnia
• Excess sweating and intolerance to heat
• Increased to excessive hunger
• Irritation, restlessness, and nervousness
• Protrusion of the eyes
• Menstrual abnormalities in women; menstruation may be irregular or short
• Abnormal heartbeat rate including rapid heart rate
• Sudden weight loss

The signs and symptoms associated with hypothyroidism may include:

• Enlarged or swollen thyroid gland; small or shrunken thyroid gland (late in the disease)
• Difficulty concentrating or thinking
• Fatigue and tiredness
• Dry skin
• Hair loss, which may be in excess while showering
• Constipation or difficult bowel movements
• Weight gain that may be slow and gradual
• Heavy and irregular periods (in women)
• Abnormal sensitivity to cold; the affected individuals may not tolerate cold very well

How is Subacute Lymphocytic Thyroiditis Diagnosed?

The diagnosis of Subacute Lymphocytic Thyroiditis may involve the following tests and procedures:

• Complete evaluation of medical history and a thorough physical examination
• Assessment of the signs and symptoms
• Blood tests to evaluate the levels of:
  • T3 and T4; thyroid hormones produced in the thyroid gland
  • Serum TSH
  • Antithyroid peroxidase antibody (anti-TPO); antibodies against thyroid peroxidase, an enzyme in the thyroid gland
  • Antithyroglobulin antibody; antibodies interacting with thyroglobulin, a protein found on the thyroid cells
• Ultrasound scans of the thyroid gland
• Fine needle aspiration (FNA) biopsy or core biopsy of the thyroid gland, if needed
• Tests and procedures to rule out any underlying condition, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Subacute Lymphocytic Thyroiditis?

Subacute Lymphocytic Thyroiditis is a generally self-limiting condition. However, sometimes, the thyroid function does not completely come back to normal levels.

Some potential complications associated with hyperthyroidism include:

• Thyrotoxicosis, or the presence of excess thyroid hormones in the body tissues
• Mental health issues such as depression
• Increased risk for heart diseases

Some potential complications associated with hypothyroidism include:

• Infertility
• Heart diseases
• Increased risk of infection

How is Subacute Lymphocytic Thyroiditis Treated?

In many cases, Subacute Lymphocytic Thyroiditis is a self-limiting condition that resolves on its own. If treatment is provided, then it is based upon the presenting symptoms:

• During the hyperthyroid stage, anti-thyroid drugs are usually not necessary
• Sometimes, thyroid hormone replacement is needed if symptoms of hypothyroidism persist and/or are severe
• Beta-blockers are known to relieve an elevated heart rate and excessive sweating, which may be prescribed if necessary
• Follow-up care with screening and check-ups are important at regular intervals

How can Subacute Lymphocytic Thyroiditis be Prevented?

The exact cause of Subacute Lymphocytic Thyroiditis is not known, and hence currently, there is no known preventive method reported for the condition. However, considering certain factors may help lower one’s risk for the same: 

• Knowledge about one’s family history is helpful in assessing future risks for the condition
• Early detection and prompt treatment of autoimmune disorders may lower one’s risk

What is the Prognosis of Subacute Lymphocytic Thyroiditis? (Outcomes/Resolutions)

• In a vast majority of cases, Subacute Lymphocytic Thyroiditis resolves on its own over a few months to a year. As the condition resolves on its own, the thyroid gland function comes back to normalcy (euthyroid state)
• Women with postpartum thyroiditis are at a higher risk for recurrence of the condition (observed in 1-6% of the cases). In rare cases, the condition may become chronic and result in chronic hypothyroidism

A close follow-up is necessary at periodic intervals; during the follow-up visits, thyroid hormone levels in blood need to be checked.

Additional and Relevant Useful Information for Subacute Lymphocytic Thyroiditis:

The following article links will help you understand thyroid-stimulating hormone (TSH), total T3, and total T4 laboratory tests:

http://www.dovemed.com/common-procedures/procedures-laboratory/thyroid-stimulating-hormone-tsh-test/

http://www.dovemed.com/common-procedures/procedures-laboratory/total-t3-blood-test/

http://www.dovemed.com/common-procedures/procedures-laboratory/total-t4-blood-test/