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Title: What must occur with T4 before it can exert its effect? Post by: ljfahey on May 17, 2013 What must occur with T4 before it can exert its effect?
Title: Re: What must occur with T4 before it can exert its effect? Post by: ARM0714 on May 18, 2013 To exert its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone, which is made in the pituitary gland located at the base of the brain, called thyroid stimulating hormone (TSH). The amount of TSH that the pituitary sends into the blood stream depends on the amount of T4 that the pituitary sees. If the pituitary sees very little T4, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the blood stream goes above a certain level, the pituitary’s production of TSH is shut off.
(http://www.thyroid.org/wp-content/uploads/images/patients/functiontests_brochure_figure1.jpg) T4 and T3 circulate almost entirely bound to specific transport proteins, and there are some situations which these proteins could change their level in the blood, producing also changes in the T4 and T3 levels. Title: Re: What must occur with T4 before it can exert its effect? Post by: ljfahey on May 19, 2013 I forgot to put what I thought the answer was, so here it is: T4 must be converted to T3 by removal of one iodine atom.
My Professor only wants simple answers and I was thinking there was more to it than what I had. Thank you very much!! |