Iodine Intake and Thyroid Function in Euthyroid Patients

General Principles for Iodine Intake

Euthyroid patients should consume adequate iodine (at least 150 mcg/day, with an upper level of 300 mcg) to maintain normal thyroid function and prevent iodine deficiency disorders, as recommended by the World Health Organization 1
Iodine deficiency remains a global health threat, causing goiter, hypothyroidism, and autonomous thyroid nodules unresponsive to TSH control, with the American Thyroid Association acknowledging the importance of adequate iodine intake 2, 3
Universal salt iodization is the WHO-recommended strategy for preventing iodine deficiency, as the iodine content in fortified salt (60 mcg/g) is very low and rarely causes toxicity, according to the World Health Organization 1

Assess iodine status by 24-hour urinary iodine excretion (normal: 100-300 mcg/24hr) combined with thyroid function tests (TSH, free T4, T3) and thyroid size evaluation, as suggested by the American College of Clinical Endocrinology 1, 2
Serum TSH alone is not a sensitive indicator of iodine status, as it usually remains within normal range despite frank iodine deficiency, with the Endocrine Society noting the importance of comprehensive thyroid function tests 2

Do not restrict iodine in healthy euthyroid patients without specific risk factors, as this increases risk of deficiency-related complications including goiter, hypothyroidism, and impaired cognitive function, as warned by the American Academy of Clinical Endocrinologists 2, 3
Be vigilant about non-dietary iodine sources including iodinated contrast agents, topical povidone-iodine disinfectants, and amiodarone, which can deliver massive iodine loads, with the European Thyroid Association recommending caution with these substances 1, 4