Thyroid Replacement Hormones

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What are thyroid replacement hormones and how do they work?

Thyroid replacement hormones are medications used to treat hypothyroidism, a condition in which the production of thyroid hormone in the body is abnormally low. Thyroid hormones increase cellular metabolism (activity of cells) that is responsible for growth, development of tissues, maintenance of brain function, body temperature regulation and several other cellular processes. Low levels of thyroid hormones in the body can result in many problems given the numerous activities that they mediate. The thyroid gland, a gland found in the lower neck is responsible for the production of thyroid hormones. It produces two main hormones, thyroxine (T4) and triiodothyronine (T3). The hormone responsible for most of the biological effects in the body is T3. When T4 is released into the blood by the thyroid gland, most of it is converted to T3 which is responsible for the cellular metabolic processes. Commercially available thyroid hormones are either natural or synthetic (man-made). Desiccated thyroid or thyroid extract (Armor Thyroid, Nature-Throid), a natural thyroid hormone is derived from beef or pork. Levothyroxine sodium (for example, Synthroid, Levoxyl and Levothroid), is the synthetic version of thyroxine (T4), liothyronine sodium (Cytomel, Triostat), is the synthetic version of tT3 and liotrix (Thyrolar) is a synthetic thyroid hormone containing a mixture of T4and T3.

Medically Reviewed by a Doctor on 5/30/2014



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