Why is my TSH rising if Free Thyroxine Index is High?

LaBigGirl · 08-30-2006, 08:09 PM

Hello, I hope this makes sense. I've got a year-and-a-half worth of thyroid bloodwork in front of me.
For years I've been on 125 mcg levoxyl daily for hypothyroidism. Since early 2005 my "Free Thyroxine Index" has read HIGH (just slightly above normal range). All other numbers are in range, so doctor is not alarmed. Even with the so-called High, I continue to feel like a dragging sloth on a daily basis. It is really hard to pull myself out of bed.
Now on the other hand my "TSH" (tells the thyroid gland to make more hormone) has been in normal range, even bordering on LOW. But recently it is creeping back up. For instance, for this year's tests:

Feb. 2006 TSH = .381

Aug. 2006 TSH = 1.837

Even though TSH remains in normal range at that level, it seems like a dramatic increase for 6 months' time, nearly 500% increase in TSH! I have used the same laboratory throughout the testings. The hospital does the analysis in-house.
When I asked my doctor how the TSH could possibly rise while my Thyroxine blood levels read "High" she just brushed it off. She just glanced at the report and said "Oh your numbers are fine." I am concerned that the thyroid gland is once again struggling to keep up with demand and the TSH is going to go up, up, and up, while I feel worse and worse, like before I was diagnosed.
Maybe someone out there could shed some light on this situation. I know I'm not as bad off as many in terms of thyroid control but this has gotten my attention. I want to feel good. Thank you!

shenacat · 08-31-2006, 01:23 AM

Check your Free T3 too. Chances are it's low during those times when your TSH is high. I would guess that at times you don't convert very well. (T4 is not the active hormone-> it converts to T3 which is active.)

LaBigGirl · 08-31-2006, 02:35 AM

You make an excellent point, Shena. Unfortunately, the thyroid panel at my lab doesn't test for Free T3 by itself. I should ask next time! But the Free Thyroxine Index can yield information about percentage of T3 uptake. The equation is:

Free Thyroxine Index (or FTI) = Total T4 x T3 Uptake percentage / 100

It appears that my body is turning enough T4 into T3, based on 31.3 % T3 Uptake (range is 22.5 to 37 % uptake). I will ask the doctor in December about this issue, now that you brought it up. Maybe for me it isn't enough T3and my body is pumping out more TSH to try to fix it. It may also explain the high-end-of-normal amounts of T4 in the blood (like you said, the non-active form). Sort of like the T4 is "all dressed up and nowhere to go!"

Thanks!

shenacat · 08-31-2006, 08:09 AM

From what I've heard, that number (FTI) is not really that reliable since it is not based on actual measurements.

LaBigGirl · 09-08-2006, 02:38 AM

Follow up: I still take levoxyl daily for hypothyroidism. I had a new TSH test this week by my general doctor, as part of some blood tests to see why I have felt horrible for months. A result copy was sent to my endocrinologist, and they called today saying the TSH was still going up, and they wanted to increase my levothyroxine a small amount. Finally!

I am so relieved this wasn't all in my head, because I started feeling bad months ago and could not get the doctor to hear my frustration. I even lied at my last endo. appt. in August and told her "I feel fine!" just to avoid being labeled depressed yet again and arguing the point with her.

I had had a thyroid profile only three weeks ago, and I am surprised that the TSH went up more in that amount of time. Now I am wondering if this new thyroid problem caused all my symptoms or just some of them, but I know this is part of the puzzle.

The lesson here is don't be discouraged by doctors who mistake your thyroid decline for a mood problem. Many of them have not experienced the "yuck" feeling of hypothyroidism (I sure wish they could!), so you need to give them the inside view of your head, how you feel. Yes, even if it means calling the office repeatedly, making inconvenient follow up appointments, and hounding them for additional blood draws.

Now with my new dose they are going to re-check in 6 weeks, and I feel as though my health is more secure. If there is another decline in thyroid function, they will be able to track it. Thanks for listening, I hope I didn't bore you with my story!