Merck Manual

Please confirm that you are a health care professional

honeypot link

Iodine Deficiency

By

Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last full review/revision May 2020| Content last modified May 2020
Click here for Patient Education

In the body, iodine (I) is involved primarily in the synthesis of 2 thyroid hormones, thyroxine (T4) and triiodothyronine (T3).

Iodine occurs in the environment and in the diet primarily as iodide. In adults, about 80% of the iodide absorbed is trapped by the thyroid gland. Most environmental iodine occurs in seawater as iodide; a small amount enters the atmosphere and, through rain, enters ground water and soil near the sea. Thus, people living far from the sea and at higher altitudes are at particular risk of iodine deficiency.

Fortifying table salt with iodide (typically 70 mcg/g) helps ensure adequate intake (150 mcg/day). Requirements are higher for pregnant (220 mcg/day) and lactating (290 mcg/day) women.

Iodine deficiency is rare in areas where iodized salt is used but common worldwide. Iodine deficiency develops when iodide intake is < 20 mcg/day.

Symptoms and Signs of Iodine Deficiency

In mild or moderate iodine deficiency, the thyroid gland, influenced by thyroid-stimulating hormone (TSH), hypertrophies to concentrate iodide in itself, resulting in colloid goiter. Usually, patients remain euthyroid; however, severe iodine deficiency in adults may cause hypothyroidism Hypothyroidism Hypothyroidism is thyroid hormone deficiency. It is diagnosed by clinical features such as a typical facial appearance, hoarse slow speech, and dry skin and by low levels of thyroid hormones... read more Hypothyroidism (endemic myxedema). It can decrease fertility and increase risk of stillbirth, spontaneous abortion, and prenatal and infant mortality.

Severe maternal iodine deficiency retards fetal growth and brain development, sometimes resulting in birth defects, and, in infants, causes cretinism, which may include intellectual disability, deaf-mutism, difficulty walking, short stature, and sometimes hypothyroidism.

Diagnosis of Iodine Deficiency

  • Assessment of thyroid structure and function

Diagnosis of iodine deficiency in adults and children is usually based on thyroid function tests Laboratory Testing of Thyroid Function The thyroid gland, located in the anterior neck just below the cricoid cartilage, consists of 2 lobes connected by an isthmus. Follicular cells in the gland produce the 2 main thyroid hormones... read more , examination for goiter, and imaging tests identifying abnormalities in thyroid function and structure. All neonates should be screened for hypothyroidism by measuring the TSH level.

Treatment of Iodine Deficiency

  • Iodide with or without levothyroxine

Infants with iodine deficiency are given levothyroxine 3 mcg/kg orally once/day for a week plus iodide 50 to 90 mcg orally once/day for several weeks to quickly restore a euthyroid state.

Children are treated with iodide 90 to 120 mcg once/day and are given levothyroxine until able to synthesize T4.

Adults are given iodide 150 mcg once/day. Iodine deficiency can also be treated by giving levothyroxine.

Women who are pregnant or breastfeeding should ingest iodide 250 mcg once/day.

Serum TSH levels are monitored in all patients until the levels are normal (ie, < 5 mcIU/mL).

Drugs Mentioned In This Article

Drug Name Select Trade
LEVOXYL, SYNTHROID
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Nutritional Requirements
Which of the following is the general recommended dietary intake of protein (in ounces) for 40-year-old men who participate in 30 to 60 minutes of moderate physical activity on a daily basis?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP