Thyroid Labs Should Be Pulled Fasting?

[Joe Sixpack]

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The doc wanted me to fast on my last lab work and I did not understand why.  All I had taken was thyroid numbers, Free T3, RT3, Free T4 and thyroid antiglobulin.  No idea why I would have to be fasting for that.  Fasting gives you much less flexibility in scheduling.  Have to report to the lab at the absolute busiest time of day

[PeakT]

The doc wanted me to fast on my last lab work and I did not understand why.  All I had taken was thyroid numbers, Free T3, RT3, Free T4 and thyroid antiglobulin.  No idea why I would have to be fasting for that.  Fasting gives you much less flexibility in scheduling.  Have to report to the lab at the absolute busiest time of day

I poked around and virtually every site said that it did not matter whether you fasted or not for thyroid tests.  However, check this out:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4171896/

"Results:

TSH was suppressed in all subjects after food irrespective of the fasting levels. Free T4 values did not change significantly. This resulted in reclassification of 15 out of 20 (75%) subjects as subclinical hypothyroidism (SCH) based on fasting values whose TSH values were otherwise within range in the postprandial sample. This may have an impact on the diagnosis and management of hypothyroidism especially where even marginal changes in TSH may be clinically relevant as in SCH and in pregnancy.

Conclusion:

TSH levels showed a statistically significant decline postprandially in comparison to fasting values. This may have clinical implications in the diagnosis and management of hypothyroidism, especially SCH."

[Joe Sixpack]

The doc wanted me to fast on my last lab work and I did not understand why.  All I had taken was thyroid numbers, Free T3, RT3, Free T4 and thyroid antiglobulin.  No idea why I would have to be fasting for that.  Fasting gives you much less flexibility in scheduling.  Have to report to the lab at the absolute busiest time of day

I poked around and virtually every site said that it did not matter whether you fasted or not for thyroid tests.  However, check this out:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4171896/

"Results:

TSH was suppressed in all subjects after food irrespective of the fasting levels. Free T4 values did not change significantly. This resulted in reclassification of 15 out of 20 (75%) subjects as subclinical hypothyroidism (SCH) based on fasting values whose TSH values were otherwise within range in the postprandial sample. This may have an impact on the diagnosis and management of hypothyroidism especially where even marginal changes in TSH may be clinically relevant as in SCH and in pregnancy.

Conclusion:

TSH levels showed a statistically significant decline postprandially in comparison to fasting values. This may have clinical implications in the diagnosis and management of hypothyroidism, especially SCH."

WOw.  Good find Peak.  I guess I do need to fast for thyroid tests!  I had no idea.

[PeakT]

WOw.  Good find Peak.  I guess I do need to fast for thyroid tests!  I had no idea.

Probably shoud be taht way for standardization.  But, on the other hand, I don't think that hardly any docs require it.

[cujet]

My Endo always has me fast for labs and not take meds just prior to the test. However, he also tests for fasting BG and other things that would otherwise be affected.

[PeakT]

My Endo always has me fast for labs and not take meds just prior to the test. However, he also tests for fasting BG and other things that would otherwise be affected.

If you guys think of it and can ask your docs next time why they do that, it would be interesting to see the actual reason they are thinking about.

[Joe Sixpack]

My Endo always has me fast for labs and not take meds just prior to the test. However, he also tests for fasting BG and other things that would otherwise be affected.

If you guys think of it and can ask your docs next time why they do that, it would be interesting to see the actual reason they are thinking about.

Yes I will try to remember that.

[ChrisCanada]

i think some docs just assume you have to fast for everything.  no pun intended, but some docs are completely clueless on thyroid and hypogonadism to begin with.

ive never fasted for mine, though i reply yes when they ask if i am fasting.. or else they won't take my blood.