Iodine deficiency and endemic goiter

A recent conversation reminded me of a fascinating case I saw last year.

An elderly Hmong woman who had recently immigrated to the United States came to see me because of an extremely large goiter. The thyroid ultrasound had shown a diffusely enlarged thyroid but without distinct nodules. As I began my interview and history, I looked at the family members in attendance. I was struck by what I observed. Of her four adult children who were present, three had easily visualized and greatly enlarged thyroids. Apparently, this was a case of endemic goiter.

Endemic goiter used to be common in the United States. Indeed, the upper Midwest was once known as the “goiter belt” in reference to the prevalence of goiter only a few generations ago. However, with iodine supplementation and consumption of non-locally produced food, endemic goiter has disappeared in the United States.

This is not the case in the rest of the world. In areas with iodine poor soils and without dietary supplementation, iodine deficiency remains common. The consequences of long-term iodine deficiency include endemic goiter and cretinism. Iodine deficiency is the leading cause of preventable mental retardation in the world. Other factors such as dietary goitrogens and selenium deficiency may also contribute to the development of endemic goiter. Areas at risk include the high mountainous areas of Europe and Asia as well as lowland areas of high rainfall such as central Africa. The Hmong are an ethnic group from the mountainous areas of southern China who reside in Thailand, Vietnam and Laos. Since the 1970s, thousands have emigrated to the United States and other countries as political refugees.

Beyond potential cosmetic concerns, endemic goiter can cause compression of the trachea or esophagus. It may be treated with radioactive iodine therapy or surgical resection depending on the severity of symptoms and the patient’s as well as clinician’s preference. Individuals with endemic goiter who relocate to areas of high iodine consumption or who are exposed to a large amount of iodine, such as from iodinated contrast, are at risk for iodine-induced thyrotoxicosis. There appears to be no increased risk of malignancy in endemic goiter.

The patient did not have any complaints. She denied difficulty swallowing or breathing. Pemberton’s sign was negative. She was not concerned because she did not think it was abnormal to have an enlarged thyroid. Her mother and grandmother had had similar goiters without problems. She was not interested in pursuing any other treatment or evaluation but did agree to have thyroid-stimulating hormone monitoring and a follow-up thyroid ultrasound in the future.

As our population becomes more diverse, it is essential for clinicians to not forget disorders that may be common in the rest of the world but rare in the United States.