Goitrogen

Goitrogens are substances that disrupt the production of thyroid hormones. This triggers the pituitary to release thyroid-stimulating hormone (TSH), which then promotes the growth of thyroid tissue, eventually leading to goiter.¹

Chemicals that have been shown to have goitrogenic effects include:

• Sulfadimethoxine (Albon),² propylthiouracil,³ potassium perchlorate,⁴ and iopanoic acid.⁵
• Some oxazolidines such as goitrin.⁶
• Ions such as thiocyanate⁷ (from cigarette smoking for example⁸) and perchlorate decrease iodide uptake by competitive inhibition and, as a consequence of reduced thyroxine and triiodothyronine secretion by the gland, cause, at low doses, an increased release of thyrotropin (by reduced negative feedback), which then stimulates the gland.
• Amiodarone inhibits peripheral conversion of thyroxine to triiodothyronine; also interferes with thyroid hormone action.
• Lithium inhibits thyroid hormone release.
• Phenobarbitone, phenytoin, carbamazepine, rifampin induce metabolic degradation of triiodothyronine (T₃) and thyroxine (T₄).

Foods which have been demonstrated to have goitrogenic effects include soy, cassava (when crushed and not detoxified by soaking,⁷) vegetables in the genus Brassica (such as broccoli and cabbage),⁹ and other cruciferous vegetables.¹⁰ The goitrogenic nature of brassica vegetables appears doubtful, particularly when accompanied by adequate dietary iodine.¹¹

In places where iodine deficiency exists in tandem with millet being a major component of the diet, millet consumption can contribute to thyroid enlargement which is the start of endemic goiter.¹²