This is because levothyroxine (chemical name tetraiodothyronine or T4) is a prohormone that needs to be converted to the more physiologically active liothyronine (chemical name triiodothyronine or T3) in the body to fully activate thyroid receptors. (thyroidpharmacist.com)
Thyroid Nodules: A Guide To Symptoms, Causes And More The Thyroid gland forms part of the endocrine system within the human body and is responsible for the secretion of particular hormones, including L - thyroxine, also known as tetraiodothyronine, and L - triiodothyronine1. (thyroidadvisor.com)
This is mainly because the thyroid is responsible for the secretion of triiodothyronine (T3), tetraiodothyronine (T4) and diiodothyronine (T2), hormones that have the ability to interact with the other hormones that are present in the body, like estrogen, progesterone and testosterone.4 (articles.mercola.com)