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Self-Assessment Questions

Endocrinology


Answer 6
  1. AIT. Amiodarone is an iodine-rich antiarrhythmic drug that has been associated with thyroid dysfunction in up to 15% of long-term users.12,13 AIT can develop suddenly, even after many years of therapy. There are 2 forms of AIT, type 1 and type 2.12,13 Type 1 AIT is a result of increased thyroid hormone synthesis and secretion and usually occurs in patients with underlying thyroid abnormalities (eg, diffuse or nodular goiter). In type 1 AIT, iodine activates thyroid hormone synthesis in autonomous areas of the thyroid gland. Type 2 AIT occurs due to release of preformed thyroid hormone and usually occurs in patients with seemingly normal thyroid glands. In type 2 AIT, amiodarone is directly toxic to the thyroid tissue and results in an inflammatory destruction of the gland and subsequent leakage of thyroid hormone into the circulation.12,13 Given the extremely high iodine content of amiodarone, a low RAIU can be seen in type 1 and type 2 AIT. RAIU is low in all patients with type 2 AIT; a normal or high RAIU excludes type 2 AIT. Thyroid function tests with Graves’ disease and TMG could be similar to those in this case. However, thyroid ultrasound in Graves’ disease usually reveals a diffusely enlarged gland with generalized hyperemia and in TMG would most likely demonstrate several thyroid nodules. Acute suppurative thyroiditis is a rare infection of the thyroid gland associated with fever, dysphagia, and thyroidal erythema and pain.

    REFERENCES
    12. Bogazzi F, Bartalena L, Gasperi M, et al. The various effects of amiodarone on thyroid function. Thyroid 2001;11:511–9.

    13. Martino E, Bartalena L, Bogazzi F, Braverman LE. The effects of amiodarone on the thyroid. Endocr Rev 2001;22:240–54.

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