A hormone that is made by the thyroid gland and contains iodine. T4 increases the rate of chemical reactions in cells and helps control growth and development. T4 can also be made in the laboratory and is used to treat thyroid disorders. Also called L-3,5,5
Thyroxine, a thyroid hormone. (The number 4 is usually in subscript.) thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. ... (12 Dec 1998) ... 
Type: Symbol Definitions: 1. Symbol for thyroxine.
T4: Thyroxine, a thyroid hormone. The number 4 is sometimes in subscript.
thyroxine.
The T4 (known to the West as the CSS-4) is a Chinese long-range, two-stage ballistic missile armed with a 5MT thermonuclear warhead. The T3 has a range of 13000 km.
Also termed tetraiodothyronine, the nickname is thyroxine. Secreted by the thyroid along with T3(triiodothyronine...confusingly shortened to thyroxine), this thyroxine is mostly conjugated in the blood by TBG (thyroxine-binding globulin), whereas the more active T3 tends to float free.