Building block of thyroid hormones and therefore important for metabolism and brain development.
Switzerland age 18–65: 150 µg/day.
Iodised salt, dairy, eggs and sea fish; seaweed contains highly variable and sometimes extreme amounts.
Goitre and hypothyroidism; in pregnancy severe deficiency increases risk of neurodevelopmental harm to the baby.
Both too little and too much iodine can trigger thyroid dysfunction.
Neck enlargement can be goitre; hair, skin and nails reflect thyroid function rather than iodine specifically.
No iodised salt, vegan diet without a fortified source, pregnancy/lactation and very limited diets.
Assess diet and thyroid clinically; single urine measurements have limited individual value.
Target by life stage and official guidance; avoid kelp/seaweed supplements because dosing is variable.
High doses can cause hypo- or hyperthyroidism and autoimmune problems.