Thyroid hormones, thyroxine (T4) and triiodothyronine (T3) are crucial for mental development in infants, body growth in young children, and metabolism in adults. While lower thyroid hormone level (hypothyroidism) causes abnormity in childhood development and low metabolism rate in adults, higher thyroid hormone level (hyperthyroidism) results in hypermetabolic symptoms including weight loss, increased heart rate, anemia and irregular heartbeats. T4 and T3 are secreted in thyroid gland in response to the stimulation by thyroid stimulating hormone (TSH). T4 level in blood is higher than T3 since T4 is produced more in thyroid and is more stable. T3 is more active and it is mostly derived from conversion of T4 by deiodinases in liver, gut, and in other organs or tissues. T3 and T4 exist in blood in active free forms and also bind with proteins to facilitate transportation.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.