Correspondence

Recognizing Iodine Deficiency in Iodine-Replete Environments

N Engl J Med 2007; 357:1263-1264September 20, 2007

Article

To the Editor:

Iodine-deficiency disorders are prevalent in regions with low iodine levels but have generally been eliminated in affluent countries through the widespread use of iodized salt.1-4 We report on two women, both lifelong residents of the United States, in whom iodine-deficiency disorders developed.

Patient 1 presented with goiter and symptoms of hypothyroidism. Examination of the neck confirmed a diffusely enlarged thyroid gland (approximately 50 g); hypothyroidism was confirmed biochemically (Table 1Table 1Clinical and Laboratory Characteristics of the Patients at Presentation.). A radioactive iodine study, performed before her referral for endocrine evaluation, was reportedly “consistent with hyperthyroidism.” The latter finding, together with a history of avoidance of iodized salt and seafood, raised suspicion of iodine deficiency. Levels of urinary iodine during a 24-hour period, which were measured in a commercial laboratory with the use of inductively coupled plasma mass spectrometry (Mayo Clinic), were markedly decreased (31 μg per day; reference range, 100 to 460). The patient was advised to use iodized salt and to add seafood to her diet. Thyroxine was not prescribed. At follow-up 2 months later, the goiter had resolved completely, and the thyroid panel had normalized (thyroxine, 6.4 μg per deciliter; thyrotropin, 2.0 μU per milliliter).

Patient 2 presented with an enlarged thyroid gland (approximately 60 g). Thyroid ultrasonography showed a diffusely enlarged gland. The left lobe measured 4.4 cm by 1.6 cm by 1.6 cm, and the right lobe measured 4.7 cm by 1.6 cm by 0.7 cm. The patient had avoided the consumption of salt ever since she had had a stroke, 7 years previously, and she rarely ate seafood. A thyroid panel was normal, but the urinary iodine was reported as “undetectable.” The patient was advised to use iodized salt and to add seafood to her diet. Two months later, a repeat urinary iodine level was normal (149 μg per day), and ultrasonography showed resolution of the goiter.

Thus, since iodine-deficiency disorders may develop in an iodine-abundant environment, information about the intake of iodized salt and seafood should be obtained routinely during the evaluation of patients with goiter. Measurement of urinary iodine excretion is warranted in suspicious cases. A pattern of diffuse uptake of radioactive iodine associated with euthyroid or hypothyroid goiter is highly suggestive of the presence of iodine-deficiency disorder, although other differential diagnoses (including the recovery phase of subacute thyroiditis) must be considered. If the condition is diagnosed promptly, dietary iodine supplementation has an antigoitrogenic effect5 and leads to dramatic resolution of iodine deficiency, thereby avoiding unwarranted lifelong thyroxine therapy in patients presenting with hypothyroidism.

Ebenezer A. Nyenwe, M.D.
Samuel Dagogo-Jack, M.D., M.B., B.S.
University of Tennessee College of Medicine, Memphis, TN 38163
sdj@utmem.edu

5 References

1. 1

   Aghini-Lombardi F, Antonangeli L, Martino E, et al. The spectrum of thyroid disease in an iodine-deficient community: the Pescopagano survey. J Clin Endocrinol Metab 1999;84:561-566
   CrossRef | Web of Science | Medline

2. 2

   de Benoist B, Anderson M, Takkouche B, Egli I. Prevalence of iodine deficiency worldwide. Lancet 2004;362:1859-1860
   CrossRef | Web of Science

3. 3

   Utiger RD. Iodine nutrition -- more is better. N Engl J Med 2006;354:2819-2821[Erratum, N Engl J Med 2006;355:1289.]
   Full Text | Web of Science | Medline

4. 4

   Caldwell KL, Jones R, Hollowell JG. Urinary iodine concentration: United States National Health and Nutrition Examination Survey 2001-2002. Thyroid 2005;15:692-699
   CrossRef | Web of Science | Medline

5. 5

   Dagogo-Jack S. A new understanding of goitrogenesis: role of cytokines in the regulation of normal and aberrant thyroid growth. Afr J Med Med Sci 1995;24:211-217
   Medline

Citing Articles (2)

Citing Articles

1. 1

   Alexander Kulczycki, Xiangbing Wang. (2009) Iodine Deficiency in Minority Populations of New Jersey. The Endocrinologist 19:2, 62-63
   CrossRef

2. 2

   Ebenezer A. Nyenwe, Samuel Dagogo-Jack. (2009) Iodine Deficiency Disorders in the Iodine-Replete Environment. The American Journal of the Medical Sciences 337:1, 37-40
   CrossRef