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Blood tests indicate hyperthyroid during treatment for hypo.

I've been on synthroid for 18 years, with doses slowly being increased due to ongoing symptoms. My doctor only ever tested TSH. This August she finally agreed to send me to a endocrinologist who tested a bunch of things. My T3 was very low. In addition to my 137mg synthroid, she added 10mg cytomel. Within 3 days, my body pain disappeared (I had no idea this was a symptom of hypothyroid, I just assumed everyone was in pain all the time as they aged) and I began having more energy. Not much, I was still requiring a nap every afternoon, but when I was awake, I felt more alert than I had in years. After 6 weeks on this combo, I had blood tests done.
TSH 0.15m/ulL(range 0.35-5)...low
FT3 5.2pmol/L(range 3.4-5.9)...normal
FT4 25pmol/L (range 12-22)...high

My endo decreased my synthroid to 125 but kept cytomel the same. I told her I was still having issues with feeling extremely cold all the time, very dry skin, sluggish, continued weight gain (which is the most troubling, as I'm an athlete and eat a very healthy diet).  
Then she told me I needed to stock up on cytomel as there were issues with supply and she wrote me another prescription in addition to the one I already had at the pharmacy. I filled it. And then I decided to see what would happen if I took another 5mg a day. What a difference!!! I was able to get off my antidepressants, I stopped sleeping with a heating pad and my winter jacket, I sleep well and wake feeling refreshed, no longer constipated, and I have energy. I wear a heart rate monitor on my sports watch which takes a reading every 10 minutes. My resting heart rate remains in the high 50's/low 60's and my BP hovers around 95/50. I haven't felt this well in 20 years.
My question is, is it possible to have blood tests indicate you have too much thyroid hormones, but not actually BE hyperthryoid? My endocrinologist said something about there being a problem with me converting T4 into T3.im so scared when I go for my next round of blood work that my numbers will be so far out of the normal range that she will take me off cytomel. I have NO signs of being hyperthryoid (she checked when I was last in her office).
Some additional info: I have a problem absorbing vitamin D, so I take high doses (under medical supervision) and have a hard time holding on to B12 (I require weekly shots to maintain my level). I also take iron daily.
3 Responses
Avatar universal
What time of day do you take your thyroid meds? What time was the blood draw for those tests?
I take synthroid and half the cytomel every morning at 6:45, and the second dose around 5:30pm.  The blood test was at 10am, but I hadn't taken my morning pills yet, because I knew not to before testing.
Avatar universal
Good that you knew not to take your med before blood draw, in order to avoid false high results.   I think the best place to start is to note that hypothyroidism is not just "inadequate thyroid hormone, but instead, it is correctly defined as "insufficient T3 effect in tissue throughout the body due to inadequate supply of, or response to, thyroid hormone".   So it is not only the supply, but the body's response, which is affected by a number of processes and variables.    So it is TISSUE T3 EFFECT that determines a person's thyroid status.  

Your FT4 was above range and higher than actually needed.   Mid-range and slightly above is adequate.   Your Free T3 of 5.2 was at 72% of the range, which is typically adequate, since the incidence of symptoms goes down with FT3 in the upper half of the range.   Your TSH being suppressed is of no concern.  When being treated with thyroid med, a suppressed TSH does not mean hyperthyroidism unless there are hyper symptoms due to excessive levels of FT4 and FT3.   Even with those levels you experience an improvement in your symptoms by adding 5 mcg of T3.    Obviously beneficial.  There are at least two possibilities I can think of that fit that scenario.    One is that everybody has different setpoints for thyroid levels art which they feel best.    Another is that by taking the added T3 you offset a deficiency in another area.  The first one that comes to mind is cortisol. It would be good to get a diurnal saliva cortisol (free cortisol) panel of  4 tests done at different times of day.  Doctors usually won't order this and will only order a morning serum cortisol (total cortisol), which is not nearly as revealing.    Along with this, whatever it takes, you need to make sure your Vitamin D is at least 50 ng/mL, and your B12 is in the upper end of its range, and your ferritin is at least 100.

If you want to confirm what I have said you can find a lot of info by clicking on my name and then scrolling down to my Journal and read at least the one page Overview of a paper on Diagnosis and Treatment of Hypothyroidism:  A Patient's Perspective.   You can also use the info in the paper, which is supported by extensive scientific evidence, to try and prevent your doctor over-reacting and reducing your med based on your suppressed TSH level.  
Thank you, this is very helpful!
Avatar universal
Hi, my experience was similar to yours, on synthroid for 17 odd years, then problems and I started researching thyroid stuff. I have been using a T4-T3 combo for 6 years now. I set my target to get my FT4 and FT3 near mid-range. Note that lab tests are not absolutely perfect, so 45 to 55% of range is acceptable to me. I got near mid-range using 100 mcg synthroid and 15 mcg compounded slow release T3 (SRT3) and fine-tuned it to 94 mcg synthroid and 15 mcg SRT3 which I have used for the last 3 years. My TSH is 2.0 average of 7 readings (lowest 1.1, highest 3.1). FYI, I am a male in my 60's and I have run 8K races on 100+10 and 94+15 combos.

You are lucky that you have an endo willing to use combos and I think she was going in the right direction to reduce your T4. I think you are right though, your FT4 and FT3 labs are likely to come back high (and TSH quite low) on the 125 T4 + 15 T3 that you are taking. Based on my experience, the solution would be to further reduce the amount of synthroid T4 that you are taking.

Here is some background information. Natural T4 (from your thyroid gland) and the T4-sythroid that you take normally gets converted to both T3 and Reverse T3 (RT3) in approximately equal amounts. But if you take too much synthroid, then your body's built-in safety mechanism kicks-in to prevent you becoming hyperthyroid. It does this by converting more and more T4 to RT3. RT3 acts as kind of a brake to T3 - and this could possibly be why you did not feel hyperthyroid.

So I turned these facts into a rule to use when taking a T4-T3 combo - if RT3 is above normal, then you are taking too much T4. By 'normal' I mean mid-point of the RT3 range. So going back to the beginning, my target was to get FT4, FT3 and RT3 near mid-range; it is hard to say if your endo will agree.

What to do? I would get labs at 4 weeks, and include RT3 if possible. If you reduce your T4, your FT4 and FT3 and RT3 will come down and TSH will go up. Be adamant with your endo that you will not reduce from 15 mcg T3 - you are getting real close to having the right combination. Good luck.

P.S. calculate the FT4, FT3 and RT3 mid-points for yourself and carry that info with you when reviewing your next labs with the endo.
Thank you so much for all these details! This make perfect sense to me.
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