Definition of color for English Language Learners. : 1  a quality such as red, blue, green, yellow, etc., that you see when you look at something. : 2  something used to give color to something : a pigment or dye. : 3  the use or combination of colors.
The thyroid hormones, triiodothyronine (T3) and its prohormone, thyroxine (T4), are tyrosine-based hormones produced by the thyroid gland that are primarily responsible for regulation of metabolism. Iodine is necessary for the production of T 3 and T 4.hyroid hormones (T 4 and T 3) are produced by the follicular cells of the thyroid gland and are regulated by TSH made by the thyrotropes of the anterior pituitary gland. The effects of T 4 in vivo are mediated via T 3 (T 4 is converted to T 3 in target tissues). T 3 is 3- to 5- fold more active than T 4.
Define thyroxine. thyroxine synonyms, thyroxine pronunciation, thyroxine translation, English dictionary definition of thyroxine. also thyÂ·roxÂ·in n. Abbr. T4 An iodine-containing hormone, C15H11I4NO4, produced by the thyroid gland, that increases the rate of cell metabolism and...