dr tsuka
Forum Junior
Topics: 12
Posts: 45
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Hi, could someone care to explain which of these hormones does the acutal inhibitory feedback? is it T3 or T4? I know that T4 is converted to T3 in the anterior pitituary, so then who is more effective at doing so? Thank you.
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| step1mom
Forum Senior
Topics: 32
Posts: 64
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T4 has more stronger affinity for the plasma binding protiens..so it is the main circulating form.Kaplan says t4 is the main circulating form so it controls negative feed back..
If levels of t3 change,increase or decrease but circulating level of t4 remains constant then TSH will remain normal too.But if circulating levels of t4 decrease that will increase TSH or vice versa...
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| GMOB
Forum Elite
Topics: 22
Posts: 250
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Yes. T4 is responsible for the majority of the (-) feedback, but when it gets to the ant. pit. it gets converted to T3 where it reduces sensitivity to TRH. Also because there is so little T3 circulating, it produces very little (-) feedback.
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| dr tsuka
Forum Junior
Topics: 12
Posts: 45
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Thank you very much! Really cleared my head!
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