AnonymousDecember 11, 1996 at 6:16 amPost count: 93172
Wow! Thank you so much for responding to my questions about T3 and T4. You were so kind to give me so much info. I printed it out so I can try and absorb it and refer back to it if needed. I have an appt. with MD tomorrow and want to see if my dose of synthyroid needs to be higher as I am tired of being tired. As someone else said on here, I have learned more here on the BB than I have from doctors. Take care and again thank you for caring!! Terri Sue in Iowa.AnonymousSeptember 15, 2003 at 8:36 amPost count: 93172
Hi, does anyone know if there is a co-relation between the numbers for TSH, T3 and T4. For the past 6 months, my T3 and T4 is in normal range but my TSH level is being suppressed. I took another lab test last week and this time, my TSH is in normal range (1.5) for the first time but my T3 and T4 is in the low end of normal range. Does that mean I am getting better from Hyperthyrodism or is the disease getting worst?AnonymousSeptember 15, 2003 at 2:04 pmPost count: 93172
The way TSH, T3 and T4 work together is this:
The thyroid produces T4 (and a little bit of T3). T4 is the inactive thyroid hormone. T4 has a life of about 6 days in the bloodstream, I think.
The body converts T4 into T3 (the active thyroid hormone) for use in the body (conversion occurs mostly in the liver, but also in other body organs to a lesser degree). T3 has a life of about 8 hours in the bloodstream.
The pituitary “reads” levels of T4 and T3 and pumps out an appropriate level of TSH (thyroid stimulating hormone) to control the output of T4 from the thyroid.
SO. When the body has too much T4 and/or T3, the pituitary stops making so much TSH. When the body has too little T4 and/or T3, the pituitary starts pumping out more TSH.
NOW, the complication. TSH is put out as something of a “running average” of our thyroid hormone levels. When our levels of T4 and T3 are changing rapidly (as they do after RAI or surgery), the TSH can lag behind somewhat, because it’s using as its thermostat the average of the levels over a certain period of time in order to judge what to send out.
I hope that gives you a little better picture of what you’re seeing when you look at your thyroid hormone tests!
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