Fast Five Quiz: Common Nutritional Deficiencies

Romesh Khardori, MD, PhD

Disclosures

February 26, 2019

Long-term dietary iodine replacement at recommended levels may decrease the size of iodine-deficient goiters in very young children and pregnant women and is indicated for all patients with iodine deficiency. Generally, long-standing goiters associated with iodine deficiency disorder respond with only small amounts of shrinkage after iodine supplementation, and patients are at risk of developing hyperthyroidism. Patients do not routinely require specific therapy unless the goiter is large enough to cause compressive symptoms (eg, tracheal obstruction, thoracic inlet occlusion, hoarseness).

Normal dietary iodine intake is 100-150 µg/day. The US Institute of Medicine's recommended dietary allowance of iodine is as follows:

  • Adults and adolescents: 150 µg/day

  • Pregnant women: 220 µg/day

  • Lactating women: 290 µg/day

  • Children aged 1-11 years: 90-120 µg/day

  • Infants: Adequate intake is 110-130 µg/day

The World Health Organization's recommendations are similar for adults and adolescents but vary for infants, children, and pregnant and lactating women as follows:

  • Pregnant and lactating women: 250 µg/day

  • Children aged 6-12 years: 120 µg/day

  • Infants to 6 years: 90 µg/day

The first sign of iodine deficiency is diffuse thyroid enlargement, which becomes multinodular over time. In patients with hypothyroidism due to severe iodine deficiency, one might see signs such as dry skin, periorbital edema, and delayed relaxation phase of the deep tendon reflexes.

UIC is not a reliable measure for assessing the iodine status of an individual because of very high variation in daily dietary iodine intake. It has been estimated that 10 UIC measurements from spot samples or 24-hour collections are required to establish an individual's iodine status with 20% accuracy. Therefore, the best diagnostic test to identify iodine deficiency in a population is a median 24-hour iodine urine collection.

If a 24-hour urine collection is not practical, a random urinary iodine-to-creatinine ratio can be used instead. In this case, a median of 50-100 µg of iodine per liter is consistent with mild iodine deficiency, 20-49 µg of iodine per liter is consistent with moderate deficiency, and < 20 µg of iodine per liter is consistent with severe deficiency.

Read more about iodine deficiency.

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