Thyroid support supplements often contain vitamins (A, D, B), minerals (iodine, selenium, zinc), and herbs (ashwagandha) to aid thyroid function, but many "support" products, especially those with glandular extracts or high iodine (like kelp), can contain actual thyroid hormones or too much iodine, potentially disrupting normal function and interfering with medical treatment. Key nutrients like selenium and iodine support hormone production, but excessive iodine (from kelp/sea moss) or unregulated supplements can be harmful; consult a doctor before taking any supplement for thyroid health to avoid complications.