Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 26-12: Iodine Deficiency Disorder & Endemic Goiter + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Common in regions with low-iodine diets High rate of congenital hypothyroidism and cretinism Goiters may become multinodular and enlarge Most adults with endemic goiter are euthyroid; however, some are hypothyroid or hyperthyroid +++ General Considerations ++ Cretinism occurs in up to 0.5% of iodine-deficient populations; less severe manifestations of congenital hypothyroidism more common Causes Iodine deficiency (most common) Certain foods (eg, sorghum, millet, maize, cassava) Mineral deficiencies (selenium, iron, zinc) Water pollutants Congenital partial defects in thyroid enzyme activity + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Thyroid may become multinodular and very large Growth often occurs during pregnancy, increasing the size of thyroid nodules and causing new nodules; compressive symptoms may occur Substernal goiters usually asymptomatic but can cause Tracheal compression Respiratory distress Dysphagia Superior vena cava syndrome Phrenic or recurrent laryngeal nerve palsy, or Horner syndrome Gastrointestinal bleeding from esophageal varices Pleural or pericardial effusions (rare) Cerebral ischemia and stroke can result from arterial compression or thyrocervical steal syndrome Malignancy in < 1% Some patients with goiter become hypothyroid Other patients become thyrotoxic as goiter grows and becomes more autonomous, especially if iodine added to diet Congenital hypothyroidism Isolated deafness Short stature Impaired mentation +++ Differential Diagnosis ++ Benign multinodular goiter Pregnancy (in areas of iodine deficiency) Graves disease Hashimoto thyroiditis Subacute (de Quervain) thyroiditis Drugs causing hypothyroidism Lithium Amiodarone Propylthiouracil Methimazole Phenylbutazone Sulfonamides Interferon-alpha Iodide Infiltrating disease, eg, malignancy, sarcoidosis Suppurative thyroiditis Riedel thyroiditis + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Serum thyroxine and thyroid-stimulating hormone (TSH) usually normal TSH low if multinodular goiter becomes autonomous in presence of sufficient iodine for thyroid hormone synthesis, causing hyperthyroidism TSH high in hypothyroidism Serum levels of antithyroid antibodies usually undetectable or low Serum thyroglobulin often elevated above 13 mcg/L +++ Imaging Studies ++ Thyroid radioactive iodine uptake usually elevated, but may be normal if iodine intake has improved + Treatment Download Section PDF Listen +++ +++ Medications ++ Dietary iodine supplementation (eg, addition of potassium iodide to table salt) Greatly reduces prevalence of endemic goiter and cretinism but is less effective in shrinking established goiter Has not proven effective for treating adults with large multinodular goiter and actually increases their risk of developing thyrotoxicosis +++ Surgery ++ Thyroidectomy indicated for cosmesis, compressive symptoms, or thyrotoxicosis in adults with very large multinodular goiters +++ Procedures ++ Patients may be treated with 131I for large compressive goiters + Outcome Download Section PDF Listen +++ +++ Follow-Up ++ Partial thyroidectomy is followed by a high goiter recurrence rate in iodine-deficient geographic areas, so total thyroidectomy is preferred when surgery is indicated +++ Complications ++ Dietary iodine supplementation increases the risk of autoimmune thyroid dysfunction, which may cause hypothyroidism or hyperthyroidism Excessive iodine supplementation increases the risk of goiter Levothyroxine supplementation May induce hyperthyroidism in individuals with autonomous multinodular goiters Therefore, levothyroxine suppression should not be started in patients with suppressed TSH levels Rarely, Graves disease can develop 3–10 months after 131I treatment in patients with large multinodular goiters +++ Prevention ++ Iodized salt contains iodine at about 20 mg per kg salt Other sources of iodine include commercial bread, milk, and seafood. The daily minimum dietary requirement for iodine is 150 mcg/day in nonpregnant adults, and 250 mcg/day for pregnant or lactating women +++ When to Refer ++ Refer to endocrinologist for hyperthyroidism, enlarging goiter, suspicious nodules Refer to thyroid surgeon for thyroidectomy for cosmesis, compressive symptoms, or thyrotoxicosis in adults with very large multinodular goiters +++ When to Admit ++ Thyroidectomy 131I treatment + References Download Section PDF Listen +++ + +Niwattisaiwong S et al. Iodine deficiency: clinical implications. Cleve Clin J Med. 2017 Mar;84(3):236–44. [PubMed: 28322679] + +Velasco I et al. Iodine as essential nutrient during the first 1000 days of life. Nutrients. 2018 Mar;10(3):E290. [PubMed: 29494508]