Joint Program in Nuclear Medicine

Isotope Imaging in Inflammatory Thyroid Disorders

Alexander Matthies, MD 
Nayer Nikpoor, MD

April 8, 1997

Presentation

A 38 year old female physician had right sided pain in the thyroid region for about 8 weeks and symptoms of hyperthyroidism for about 3 weeks prior to presentation. The T4 was greater than 24 mg/dl, TSH was less than 0.1 uU/ml, ESR was markedly elevated at 97. A thyroid scan was obtained.

Imaging Findings

A Tc-99m Pertechnetate thyroid scan revealed an enlarged gland with minimal uptake. Subacute thyroiditis was diagnosed, most likely of the granulomatous type.

Discussion

Inflammatory thyroid diseases account for about half of all clinical thyroid disorders. The differential diagnosis includes: History (including medication, diet), physical examination, thyroid function test, antibody screening, WBC and ESR are most helpful in differentiating the different types of thyroiditis.

Chronic lymphocytic thyroiditis (Hashimoto)

Chronic lymphocytic thyroiditis (Hashimoto) is the most common inflammatory thyroid disorder as well as the most common cause of goiter in the US. It is an autoimmune disorder with high levels of antibodies against thyroid peroxidase and - less frequent - against thyroglobulin. The highest incidence occurs in middle aged women, who usually present with a non-tender goiter and who are biochemically either euthyroid or hypothyroid. A thyroid scan provides only limited additional information. It usually shows patchy uptake and occasionally hot or hot and cold nodules.

Subacute lymphocytic thyroiditis

Subacute lymphocytic thyroiditis is also an autoimmune disorder, that occurs most frequently in women after delivery (3 to 16%), rarely in sporadic cases. Thyroid peroxidase antibodies can nearly always be found. Patients initially present with hyperthyroidism and a painless goiter. In the acute phase there is minimal or absent uptake of Pertechnetate or Iodine in the gland, which allows differentiation from Grave's disease. After a variable period of weeks to months the patients become briefly euthyroid and than hypothyroid. Treatment includes the control of clinical symptoms of hyper- and hypothyroidism, until resolution of the inflammatory process has occurred.

Subacute granulomatous thyroiditis (De Quervain)

Subacute granulomatous thyroiditis (De Quervain) usually follows an upper respiratory tract infection and has most likely a viral etiology. It is more common in females with a peak incidence between 30 and 50. Antibodies against thyroglobulin, peroxidase or TSH receptor are only transiently elevated or normal. Sudden or gradual onset of pain over the thyroid gland and a high ESR are features, that usually distinguish it from subacute lymphocytic thyroiditis. The initial phase of hyperthyroidism with a diffusely decreased uptake on thyroid scan should be treated with salicylates or steroids. Following successful treatment the patients become usually hypothyroid and most regain a normal thyroid function after about 4-6 months, while about 5% become permanently hypothyroid.

Acute suppurative thyroiditis

Acute suppurative thyroiditis is a very rare disorder. In nearly 70% of cases it is due to bacterial infection of the thyroid gland, most frequently Staphylococcus aureus, Streptococcus pyogenes and Pneumococcus pneumoniae. Mycobacterial, fungal and other pathogens are usually seen in immunocompromised patients. Patients have typically severe systemic and local symptoms. Thyroid scan is usually normal, unless abscess formation has occurred.

Conclusion:

Thyroid scanning provides in most inflammatory disorders only limited new information in addition to history, physical examination and biochemistry. Thyroid scanning can be helpful in particular situations, i.e. in the differentiation of Grave's disease from subacute lymphocytic or granulomatous thyroiditis in hyperthyroid patients. Radioactive iodine uptake with or without scanning is a good way to monitor thyroid function in patients with subacute granulomatous thyroiditis during treatment.

References

1. Farwell A P, Braverman L E : "Inflammatory thyroid disorders" in Otolaryngologic Clinics of North America, 1996; 29: No 4

2. Blum M et al.: "The Thyroid" in Wagner et al: "Principles of Nuclear Medicine" 2nd ed, 1995, W B Saunders

3. Wang P et al. : "Tc-99m Pertechnetate Trapping and Thyroid function in Hashimoto's thyroiditis" , Clin Nuc Med 1994; 3: 177-180

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J. Anthony Parker, MD PhD, Tony_Parker@bidmc.harvard.edu