Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are iodine-containing hormones produced by the thyroid gland that regulate metabolism, growth, and development. They are crucial in clinical practice for diagnosing and managing disorders such as hypothyroidism and hyperthyroidism, which can significantly impact cardiovascular, neurological, and metabolic function. An important clinical association is that abnormal thyroid hormone levels can lead to complications like atrial fibrillation in hyperthyroidism or myxedema coma in severe hypothyroidism.