Fluctuating TSH & T4

[Rite760]

Dear Dr Lupo, I'm so sorry to bother you again. But you explained to me last month that TSH responds more quickly whereas T4 takes time to show a response to a fluctuation in TSH and I can understand that. But I want to ask you why this month's results don't make sense. Last month my TSH was 3.8 which you said was borderline hypothyroid and my T4 was 17 (UK Range is 11 to 26) so although the TSH was out, the T4 was considered normal. This month the T4 is low at 10 which I can now understand is a reflection on the time it has taken for it to show a response to the high TSH of 3.8 the month before. However, although the T4 is now considered at 10 as hypothyroid, the TSH this month has dropped again to 2.2, which is considered as normal! Please can you explain why this is, and why both of them don't correspond at the same time together Or why they won't just stay at the same time showing hypothyroid results  like the rest of my family. Thank you so much and sorry for bothering you again.

[Mark Lupo, M.D.]

That's more of a fluctuation than we usually see.  I do not have a straight-forward explanation for this unless it relates to timing of levothyroxine dose.  The TSH is the more important lab - sometimes looking too much into the numbers is not very helpful and can be frustrating.  If the TSH is okay, would not worry that much about a slightly off T4.

[authrjenn]

Stop by the site ****.***  It will explain all about Armour thyroid meds.

[BobbyWayne]

I have been off levithroxin for 5 weeks and now am on Armour Thyroid 30 mg.  Is there a period of adjustment from beginning the new thyroid med until it reaches max effect??:? If so approx how long.Thanks