Iodine deficiency
Symptoms, at-risk groups, and clinical context for iodine deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.
Iodine deficiency was once endemic in the US Midwest 'goiter belt' but largely eliminated by salt iodization beginning in 1924. It remains one of the world's most common preventable causes of intellectual disability — severe deficiency during pregnancy causes irreversible brain damage and cretinism in offspring. Mild-to-moderate iodine deficiency is re-emerging in some US groups due to reduced iodized salt use and increased processed food consumption.
Common symptoms
- Enlarged thyroid (goiter) — visible swelling at the front of the neck
- Fatigue and lethargy
- Weight gain, cold intolerance
- Dry skin, brittle hair, hair loss
- Constipation
- Memory or concentration problems, depression
- Heavy or irregular menstrual periods
- Slowed heart rate (hypothyroid symptoms)
- In severe maternal deficiency: miscarriage, stillbirth, intellectual disability or cretinism in offspring (IRREVERSIBLE)
At-risk groups
- Pregnant and breastfeeding women (requirements increase to 220-290 µg/day; ATA recommends 150 µg supplemental)
- Women planning pregnancy (fetal brain development depends on adequate iodine from week 1)
- People avoiding iodized salt (sea salt and kosher salt typically aren't iodized)
- People on strict vegan diets (limited dairy and fish, both major sources)
- People avoiding dairy (lactose intolerance, dairy allergy) without replacement sources
- People in regions with selenium-deficient soils (selenium needed for thyroid hormone metabolism)
- People consuming large amounts of goitrogenic foods (raw cruciferous vegetables, soy) without adequate iodine
When to see a doctor: Visible neck swelling, persistent fatigue with cold intolerance, or unexplained weight gain warrants TSH and possibly free T4 testing. CRITICAL: anyone planning pregnancy or in early pregnancy should ensure adequate iodine — most prenatal vitamins contain 150 µg, but check the label. Severe maternal iodine deficiency damages the fetal brain in the first trimester, often before pregnancy is recognized. Note: excessive iodine (especially from kelp supplements) can also disrupt thyroid function — moderation matters.
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Related deficiencies
Nutrients with overlapping symptoms — useful when investigating an unclear clinical picture.