The thyroid is a butterfly-shaped gland crucial for hormone production affecting metabolism, heart rate, and more. Signs of thyroid issues include weight changes, irregular heartbeat, and temperature sensitivity. You can live without a thyroid with hormone therapy. Key hormones include T3, T4, RT3, and calcitonin. Iodine is essential but must be balanced. Thyroid disease affects 20M+ Americans—main types include hypothyroidism and hyperthyroidism. Women are especially at risk