Goitrogens are substances that disrupt the production of thyroid hormones. In response, the pituitary increases the release of TSH, which stimulates growth of the gland tissue and can lead to a goiter (hence the name, from the Latin guttur — throat).
They act in different ways: some (thiocyanates, perchlorates) competitively hinder iodine uptake by the thyroid gland, others block the incorporation of iodine into hormones. For most people with adequate iodine intake, ordinary portions of such foods are safe.
Where goitrogens are found
Dietary goitrogens are found in cruciferous vegetables (cabbage, broccoli, cauliflower, turnip) — through glucosinolates and their breakdown products (goitrin, isothiocyanates), in soy (isoflavones), in millet, and also in cassava, from which thiocyanate is released when it is insufficiently processed. A potent source of thiocyanate is tobacco smoking.
Cooking reduces goitrogenic activity: heat inactivates the enzyme myrosinase and reduces the formation of active compounds, so boiled vegetables are less "goitrogenic" than large amounts of raw ones.
When it matters
Clinically, goitrogens matter mainly against a background of iodine deficiency or when consumed in very large amounts — then they worsen the iodine shortage and contribute to hypothyroidism and goiter. With adequate iodine, the goitrogenic effect of ordinary vegetables is considered doubtful, and their benefit outweighs it.
People who already have reduced gland function or who take levothyroxine (free T4 is the treatment marker) should ensure adequate iodine and not overindulge in raw soy and large volumes of raw cruciferous vegetables, and should take soy and iron/calcium supplements separately from levothyroxine. Thyroid calculators help assess how the gland is working.
Calculate using this marker
Calculators where Goitrogens is used directly:
Frequently asked questions
Do I need to give up cabbage and broccoli for the sake of the thyroid?
No. With adequate iodine intake, ordinary portions of cruciferous vegetables are safe, and cooking further lowers goitrogenic activity. Caution is needed only with iodine deficiency or very large amounts of raw vegetables.
Is soy bad for the thyroid gland?
In people with normal gland function and adequate iodine, moderate soy consumption does no harm. But soy can reduce the absorption of levothyroxine, so the drug is taken separately from soy, several hours apart.