Overmedicated/undermedicated?!

[Melodica8]

Hi, sorry for the long waffley post- I will try to keep it succinct.

I was started on 50mg thyroxine last October. My t4 was within range but right down the bottom, and was symptomatic. In December it was increased to 75mg after fasting bloods (it was around 17, ref range 12-22). Last week went to see my GP as felt awful, really woozy, anxious, tired. Managed to get bloods done that day- showed my T4 was very slightly over range. (22.9) Would have been about 4 hours after my morning dose) so told to cut down to 50mg. Which I don’t feel is enough- I’m feeling lethargic, brain fog, anxious and getting awful headaches every day everyday, usually starting in the afternoon. Bloods also showed I was Vit D deficient. So now I’m really confused! Are the headaches due to lower levo? Will my TSH kick in a bit more and stimulate my thyroid? Or do I just need an awkward dose like 65mg?! 😳 seeing my endo in March, after repeat b/t. My gp wants to up my sertraline for the anxiety. I feel a mess! 😩

Most recent bloods:

T4 22.7 pmo/L (12-22)

Free T3 5.3 pmo/L (3.1-6.8)

TSH 0.07 mu/L (0.27-4.20)

Vit D 40nmo/L (50-120)

Serum ferritin 115 (13-150)

B12 306 ng/L (197-771)

Also on 100mg sertraline and 1500mg metformin.

[greygoose]

Your doctor should not have reduced your dose because your FT3 was not over-range, and that is the most important number. It was only just over mid-range, because you don't convert very well. It will now be even lower, and it is low T3 that causes symptoms. You are now under-medicated.

[Melodica8 in reply to greygoose]

That’s exactly what I was thinking, when I posted the results earlier. Didn’t realise I don’t convert well- although that does make sense if I’m at top range for t4 but not for t3. I’ve taken the other 25mg this evening and I feel better, head has cleared and fog lifted. Would the levo have been causing my whoozy symptoms last week though? Or maybe that is just anxiety and I should up my sertraline. This is so confusing! Would you recommend not taking levo before my next fasting b/t?

[greygoose in reply to Melodica8]

You took your levo before your blood draw? How long before? That would give you a false high FT4. Wouldn't affect TSH or FT3, though. You should leave a gap of 24 hours. So, perhaps you don't have a conversion problem, after all.

It's more likely to be low T3 causing your symptoms than the levo itself.

[Melodica8 in reply to greygoose]

Yes it was an unexpected blood test, I went to see gp with symptoms, she managed to get a blood test appointment straight after- so it was about 5 hours after I’d taken levo.

[Hidden in reply to greygoose]

GG, are you saying that FT4 levels peak in the same way FT3 levels do after taking drugs? I have always believed the reason we should avoid taking NDT or synthetic T3 before having labs was because FT3 levels will peak very quickly after taking hormones (2-3 hours) and then fall rapidly, whereas T4 levels remain steady as T4 has a half-life of several days (as opposed to T3). And isn't the T4 to T3 conversion an ongoing process that won't look much different right after you've taken your levo compared to 24 h after taking any...? After all, most of the conversion takes place outside the thyroid gland. Or did I misunderstand you?

[helvella in reply to Hidden]

T4 definitely peaks - typically around two hours or so after ingestion. In some people that could be slower to reach the peak. It then drops slowly over several hours.

When absorbed, the T4 is free, so it is the Free T4 that is particularly affected after taking a tablet. In time, the increased FT4 becomes bound (or is otherwise processed) so the FT4 does drop.

[Hidden in reply to helvella]

Interesting, thanks!