T4 and T3 hormones are essential for the body to function. They are produced by the thyroid gland in the neck and serve to regular many processes in the body. Increasing levels of thyroid hormone increase the rate of cellular metabolism while low levels can slow things down dramatically. The thyroid gland produces these hormones very effective and takes iodine, found in many foods that people eat, and convert it into the thyroid hormones. These two hormones are called thyroxine (T4) and triiodothyronine (T3). The thyroid cells are the only cells in the body which can take in iodine and process it properly in order to make use of it.
These cells use a special mechanism to combine iodine and special proteins to make the thyroid hormones. These hormones are stored and packaged for later release. When the T3 and T4 are released into the blood stream, they are transported throughout the body. In the different organs and tissues they control the rate of cellular metabolism (which is the conversion of oxygen and calories to energy). Every cell in the body depends upon thyroid hormones for modification of their metabolism. The thyroid can tell the organs and tissues to speed up or slow down depending on what is going on with the body.
The normal thyroid gland produces much more T4 and a small amount of T3. But while the hormone is circulating in the body, a lot of T4 is converted to T3. Also, it is important to know that T3 possesses about four times the hormone “strength” as T4, therefore it is much more potent and can exist in much smaller quantities. Known the normal t4 and t3 levels is therefore essential to understanding the functioning of the thyroid gland. This gland is modified by other systems as well. The thyroid and the pituitary are part of the endocrine system. This gland system also includes the pancreas and the adrenals. The sex glands such as the testes and ovaries are also part of the endocrine system as well at the reproductive system.
The thyroid gland is actually under the control of the pituitary gland, which is a small gland the size of a little nut at the base and is positioned at the base of the brain. When the level of thyroid hormones (T3 & T4) decreases too much and get too low, the pituitary gland produces a hormone called Thyroid Stimulating Hormone (TSH). This compound actually stimulates the thyroid gland to produce more hormones and also to release them into the blood stream. When the level of the hormone gets too high, the TSH production decreases. This causes the production of the T3 and T4 hormones to decrease as well. This forms what is called a ‘negative feedback loop’ which serves to regulate essential body processes. A lot of different functions are in these negative feedback loops. With this information, a person can very effectively know about their t4 and t3 hormones and improve their overall state of health through the improvement of their thryoid hormone status.