Overview of thyroiditis

If hypothyroidism is present, levothyroxine (Euthyrox, Eltroxin) should be given in usual replacement doses (0.05 – 0.2 mg orally daily)....
Maha Khalifa, BS Pharm, PharmD, BCPS, MSc

INTRODUCTION ㅡ Thyroiditis is an inflammatory disease of the thyroid, with different etiologies and different clinical characteristics according to disease stage. They include conditions that cause acute illness with severe thyroid pain (e.g., subacute thyroiditis and infectious thyroiditis) and conditions in which there is no clinically evident inflammation and the illness is manifested primarily by thyroid dysfunction or goiter (e.g., painless thyroiditis and fibrous [Riedel's] thyroiditis).

CLINICAL PRESENTATION

AUTOIMMUNE THYROIDITIS ㅡ Thyroid gland may be diffusely enlarged, firm, and finely nodular but is frequently not palpable. One thyroid lobe may be asymmetrically enlarged, raising concerns about neoplasm. Symptoms and signs are mostly related to levels of thyroid hormone. Affected patients may have combinations of hyperthyroidism and hypothyroidism. Depression and chronic fatigue are more common. About one-third of patients have mild dry mouth (xerostomia) or dry eyes (keratoconjunctivitis sicca) related to Sjögren syndrome.

  • Postpartum thyroiditis. Typically manifested by hyperthyroidism that begins 1–6 months after delivery and persists for only 1–2 months. Hypothyroidism tends to develop beginning 4–8 months after delivery.

    Painless sporadic thyroiditis. Thyrotoxic symptoms are usually mild. Small, nontender goiter may be palpated in about 50% of such patients. Course is similar to postpartum thyroiditis.

PAINFUL SUBACUTE THYROIDITIS ㅡ Presents with an acute, usually painful enlargement of the thyroid gland, often with dysphagia; pain may radiate to the ears. Low-grade fever and fatigue are usually present. Manifestations may persist for weeks or months and may be associated with malaise. Normal thyroid function typically returns within 12 months, but persistent hypothyroidism develops in 5% of patients.

INFECTIOUS SUPPURATIVE THYROIDITIS ㅡ Patients usually are febrile and have severe pain, tenderness, redness, and fluctuation in the region of the thyroid gland. In IGG4-RELATED THYROIDITIS, thyroid enlargement is often asymmetric; the gland is stony hard and adherent to the neck structures, causing signs of compression and invasion, including dysphagia, dyspnea, pain, and hoarseness. Related conditions include retroperitoneal fibrosis, fibrosing mediastinitis, sclerosing cervicitis, subretinal fibrosis, and sclerosing cholangitis.

DIAGNOSIS

Table (1). Diagnosis of Thyroiditis
INVESTIGATION COMMENT
Laboratory Findings Serum levels of TSH are suppressed in hyperthyroidism due to thyroiditis.
Autoimmune thyroiditis
  • Circulating levels of the antithyroid antibodies TPO Ab (90%) or Tg Ab (40%) usually increased.
  • However, about 5% of patients have no detectable antithyroid antibodies.
  • Serum FT4 levels tend to be proportionally higher than T3 levels.
Painful subacute thyroiditis
  • ESR is markedly elevated.
  • Antithyroid antibody titers are low.
  • Serum FT4 levels tend to be proportionally higher than T3 levels.
Infectious suppurative thyroiditis Both the leukocyte count and ESR are usually elevated.
Imaging
  • Ultrasonography
      • Helps distinguish thyroiditis from multinodular goiter or thyroid nodules that are suspicious for malignancy.
      • It is also helpful in guiding FNA biopsy of small suspicious thyroid nodules.
  • Color flow Doppler ultrasonography can help distinguish thyroiditis from Graves disease.
  • Radioiodine (RAI) uptake and scan can help distinguish thyroiditis from Graves disease.
  • [18F] Fluorodeoxyglucose positron emission tomography (18FDG-PET) scanning frequently shows diffuse thyroid uptake of isotope in cases of thyroiditis.

MANAGEMENT

AUTOIMMUNE THYROIDITIS (HASHIMOTO) ㅡ If hypothyroidism is present, levothyroxine (Euthyrox, Eltroxin) should be given in usual replacement doses (0.05–0.2 mg orally daily). In patients with a large goiter and normal or elevated serum TSH, an attempt is made to shrink the goiter with levothyroxine in doses sufficient to drive the serum TSH below the reference range while maintaining clinical euthyroidism.

          Dietary supplementation with selenium (Selenium ACE, Selenium Extra) 200 mcg/day reduces serum levels of TPO Ab. Simvastatin (Zocor) 20 mg orally daily improved thyroid function over 8 weeks in patients with autoimmune thyroiditis and subclinical hypothyroidism.

PAINFUL SUBACUTE THYROIDITIS ㅡ The drug of choice is aspirin (325–650 mg orally every 4–6 hours, which relieves pain and inflammation) or NSAIDs. For patients with severe pain, prednisone (Solupred), 20 mg orally daily for about 2 weeks, can be effective. Thyrotoxic symptoms are treated with propranolol (Inderal), 10–40 mg orally every 6 hours. Transient hypothyroidism is treated with T4 (Euthyrox) 50–100  mcg orally daily if symptomatic.

INFECTIOUS (SUPPURATIVE) THYROIDITIS ㅡ Treatment is with antibiotics and with surgical drainage when fluctuation is marked. Immunocompromised individuals are particularly at risk and coccidioidomycosis thyroiditis has been reported. Surgical thyroidectomy may be required.

IGG4-RELATED THYROIDITIS (RIEDEL THYROIDITIS) ㅡ The treatment of choice is tamoxifen (Nolvadex), 20 mg orally twice daily, which must be continued for years. tamoxifen can induce partial to complete remissions in most patients within 3–6 months. Short-term corticosteroid treatment may be added for partial alleviation of pain and compression symptoms. Rituximab (Mabthera) may be useful when tamoxifen and corticosteroids fail.

note
  • Levothyroxine (Euthyrox) is given orally in the morning in an empty stomach 30-60 min before food, may be administered at night 3-4 hours after last meal, don’t administer within 4 hours of calcium or iron containing product, don’t crush or chew and monitor serum thyroid-stimulating hormone initially every 6 to 8 week.
  • Suppurative thyroiditis: Use IV antibiotics and drain abscess (if present) in patients.
  • Surgical referral in patients with compression of adjacent neck structures and in some patients with infectious (suppurative) thyroiditis.
  • Total thyroidectomy has been shown to improve symptoms in patients with Hashimoto thyroiditis who still have symptoms despite having normal thyroid gland function while receiving medical therapy.

REFERENCES