Resolved question:
Hi,
I wanted a second opinion regarding a thyroid blood test. Both my t3 and t4 counts were low (out of range) in my blood test, but my TSH was within range (though a little low within the acceptable range). My general practitioner said the only count that mattered was the TSH, as t3 and t4 can vary too much over the course of the day. I didn't really understand this explanation as from my limited understanding TSH is what stimulates the thyroid but t3 and t4 is what the thyroid actually produces, so I would think the "output" of the thyroid (t3 and t4) would be an indication of hypothyroidism.
I wanted a second opinion on this, since hypothyroidism runs in my family (my mom has it and takes medication for it) and some symptoms I have had recently match hypothyroidism (chronic constipation, sleeplessness, cold hands and feet, lack of tolerating cold outdoor temperatures).
Submitted:
4 Days
Category:
Family Physician-GP
Hello,
Thank you for your query at DoctorSpring.com
I understand your concern.
Thyroid hormone abnormalities are a little tricky to diagnose. In most cases, TSH is the most important parameter. A high TSH with normal T3, T4 or low T3, T4 levels indicate that the patient has hypothyroidism. TSH is stimulated by a feedback mechanism, hence if the thyroid values are intrinsically low, then TSH will shoot up leading to stimulating the thyroid hormone further increasing the output. In hyperthyroidism, TSH will be low, and T3, T4 will be high.
So your GP is right, in explaining that TSH is more important than the values of T3, T4 which actually varies throughout the day.
You can attach your reports for me to review and I can guide you accordingly.
Hope this was helpful,
Dr. Jay