Levoxyl and Cytomel dosage changed after weird test results . Does it make sense?

[Oldie68]

I was diagnosed with Hashimoto's in 2017 and have been on 100 mcg Levoxyl for about 5 years. Two years ago I finally convinced the fourth endocrinologist I was seeing to add Cytomel (5mcg). I immediately started feeling better, physically and mentally. Early this year I was diagnosed with advanced metastatic prostate cancer. I had chemotherapy with docetaxel for about 5 months.

Prior to chemo my results were

TSH 2.89 uIU

Free T4 1.2 ng/dL

Total T3 46 (51) ng/dL (two results taken one day apart)

After chemo

TSH 0.19 uIU (normal range is 0.55 - 4.78)

Free T4 1.2 ng/dL (normal range is 0.9 - 1.8)

Total T3 30ng/dL (normal range is 60 - 181)

Endocrinologist reduced my Levoxyl to 75 mcg/day and doubled the Cytomel to 10 mcg/day. I don't understand the low TSH because my T4 seems to be normal.

So my questions are:

1. Why lower the Levoxyl when my T4 is normal?

2. What is the cause of TSH being low? Is my pituitary gland not working?

3. Why double the Cytomel?

Thank you for reading.

[greygoose]

1. Why lower the Levoxyl when my T4 is normal?

Two possible reasons:

a) Because doctors are terrified of a below-range TSH. They believe it causes heart attacks and osteoporosis. It doesn't, but that's what they learnt in med school, so they only tend to look at the TSH and ignore the rest. And they've never understood that if you're taking T3, reducing T4 isn't going to raise the TSH.

b) Because they believe that's what you have to do when increasing the T3 dose. There's no logic to it, but that's what they learnt in med school and they don't think about the necessity - or lack of it - they just do it automatically.

2. What is the cause of TSH being low? Is my pituitary gland not working?

The cause is taking T3. That's what it does. And it happens because the pituitary senses that you're taking T3, and that therefore, you don't need TSH anymore.

3. Why double the Cytomel?

Because your T3 was below range. And, because T3 is increased 5 mcg by 5 mcg.

Edit: I thought I should just mention that TT3 is the wrong test. They ought really to test Free T3. TT3 - Total T3 - includes T3 that is available for your body to use, plus T3 that isn't available because it's bound to a protein. Ideally, we want to know how much we have available straight away. The results could be completely different. But, your TT3 is very low, which is not surprising after cancer and chemo.

[Oldie68 in reply to greygoose]

Thank you for your response. Every endo I have talked to says that testing for Free T3 is "unreliable". They can't explain why but the answer is always the same. I only succeeded in convincing one endo to test free T3 and that's when I got the prescription for Cytomel. The Free T3 turned out to be below normal.

[greygoose in reply to Oldie68]

That's just an excuse. The truth is that They don't understand what T3 is or what it does. It's true that T3 levels have a circadian rythme, but it doesn't vary nearly as much as the TSH! And yet they rely entirely on the TSH to judge thyroid status. Thing is, they don't really know what they're doing.

But, they learnt certain things in med school, and they just recite them like parrots, with no understand of why or how. They don't question anything. Unlike those of us that have to live with this wretched disease!

Anyway, at least you got an increase in your dose of T3, so let's hope that helps.

[Oldie68 in reply to greygoose]

I am not sure I need the 10 mcg/day Cytomel. I was feeling fine on 5mcg/day, even when skipping for a day or two. I thought that the TSH responds to T4 levels, not T3. Is this wrong?

[greygoose in reply to Oldie68]

I'm afraid it is. TSH responds to both - but much more strongly to T3. Taking T3 will almost always suppress TSH, or take it below range.