Free T4 and TSH Fluctuations

[thebeag]

Hi, all.

Got some new tests done which show fluctuations in Free T4 and TSH over short periods of time (same pattern occurs over long periods of time). Results are below.

Note that Free T4 and TSH move in the same direction. All tests were performed in same lab, at same time of day and while fasting. I am not on any thyroid medications, tested negative for thyroid antibodies (TPO and Thyroglobulin antibodies), and FreeT3 has always been within range (averaging in bottom third of range). Thoughts? Is this worth pursuing? Appreciate any words of wisdom you can share.

1/12/2019

TSH = 1.71 (.45 -4.5)

FreeT4 = .55 (.8 -1.7)

1/23/2019

TSH = 2.47 (.45-4.5) - 44.4% increase

FreeT4 = 1.2 (.8 -1.7) - 118% increase

2/6/19

TSH = 1.81 (.45 - 4.5) - 26.7% decrease

FreeT4 = .95 (.8 - 1.7) - 20.8% decrease

[dorob]

This represents normal fluctuation. A healthy thyroid, without medication, will respond to your bodies needs. The fluctuation in T4 are known to be that dramatic over a 24 h period and will vary between days. A person on medication has more stable levels because the thyroid does not respond, and instead, the person relies on a steady stream of drug for all his or her needs.

[thebeag in reply to dorob]

Thanks, dorob. That makes sense. A quick follow-up, if you don't mind. When the thyroid adjusts to the body's needs, will we see FreeT4 and TSH move in the same direction (both increase or both decrease)? Does the well-known inverse relationship between TSH and FreeT4 only hold in disease states?

[dorob in reply to thebeag]

Essentially, yes. The problem with your results are that they are like a medicated person stopping therapy and then medicating with more. Thus, the TSH may reflect a previously low T4 that has been increased. TSH increases T4 levels, so the 2 rise normally together in health states. in disease, the TSH rises in an attempt to flog the dead thyroid gland, which spews out less and less T4 in its death throes.

[thebeag in reply to dorob]

Got it. Makes perfect sense now! Thank you.