Iodine

Iodine is the fundamental building block of thyroid hormones T3 and T4 — without adequate iodine, the thyroid literally cannot produce its hormones. Iodine deficiency is the leading cause of preventable hypothyroidism worldwide, and mild deficiency is more common than most people realize even in developed countries. Iodine is also critical during pregnancy for fetal brain development — the WHO recommends 250 mcg daily during pregnancy and breastfeeding.

Women with hypothyroidism (especially if not from autoimmune disease), vegetarians/vegans (limited iodine food sources), and all pregnant and breastfeeding women.

150 mcg daily for non-pregnant women. 220–250 mcg during pregnancy. 290 mcg during breastfeeding. Iodized salt and dairy are common dietary sources.

Thyroid function can improve within weeks of correcting deficiency, but full hormonal normalization takes months.

Very safe at recommended doses. Paradoxically, very high doses of iodine can worsen certain thyroid conditions (Hashimoto's, hyperthyroidism).

Women with Hashimoto's thyroiditis should be very cautious with iodine supplementation — excess iodine can trigger thyroid flares. Always consult your endocrinologist.