Reverse T3 question (thyroid)

[DebE13]

This isn't MC related but is beneficial in attempting to determine the cause of on-going issues with fatigue. My PCP was agreeable to testing my RT3. I found the ratio calculator on the Stop the Thyroid Madness website and mine is at 19.5.

https://stopthethyroidmadness.com/rt3-ratio/

My recent labs came in with:
FT4 1.2 ng/dL 0.9 - 1.5 ng/dL
FT3 3.3 pg/mL 2.4 - 4.1 pg/mL
RT3 16.9 ng/dL
TSH 0.01 uIU/mL 0.60 - 5.40 uIU/m

Am I correct in interpreting that I do not have a pooling issue? I take 150mg of Armour daily and that is as high as my PCP will go. He told me he doesn't want to chase numbers. I get where he is coming from but have on-going symptoms that are difficult to pin down if it's related to my thyroid, MC, fibro, lyme's, etc. I'm thinking it's a safe assumption to focus on my guts and nutritional deficiencies?

It's slightly below the "normal" mark but I doubt it's even worth bringing up again at my appointment next week.

Am I missing anything?

[tex]

Yes, using the calculator you cited, I get 19.5, which is only slightly lower than the stated reference lower limit of 20.

However, 1 ng/dl = 10 pg/ml. Therefore 16.9 ng/dl = 169 pg/ml. So your RT3/FT3 ratio is 169/3.3 = 51.21. Dr. Amy Myers prefers that the ratio be less than 10.

What Your Thyroid Lab Results Really Mean

So who's right?



Tex

[DebE13]

Good article but makes me more confused. My FT4 and FT4 numbers are close to that feel-good range but then the ratio is off. How can dosage be adjusted that will correct one but then throw off other?

My brother just had an ultrasound of his thyroid and now has to have an FNA. I am praying he isn’t about to go down this road.

[tex]

Deb,

I doubt that your RT3 is anything to be concerned about. Without a thyroid your normal numbers may need to be different than what Dr. Myers discussed. She was surely talking about patients with intact thyroid glands.

Tex

[TM]

Tex and Deb,

As usual I’m still confused after reading both references, and don’t understand why Deb’s RT3 value needs to be converted to pg/mL to match the FT3 units used in the other half of the equation.
Myers listed her optimum thyroid ranges using the same types of units that Deb did, and I couldn’t find anything on Myers’ webpage calling for any of the values to be converted.
But the first thing I noticed on the “Thyroid Madness” website was this warning:
IF BOTH OF YOUR MEASUREMENTS ARE pg/mL:  you may get a double or triple digit number, and that means it’s missing a decimal. For example, 83 may be 8.3. 
THE FT3/RT3 ratio chart on the “thyroid madness” site has a dropdown menu, allowing a computation using both units: pg/mL and ng/dL and as indicated, Deb’s FT3/RT3 ratio works out to: 3.3/16.9 = 19.5

So to get the RT3/FT3 ratio that Myers says should be <10, why wouldn’t you just switch the top and bottom of the “thyroid madness” equation, FT3/RT3 to: RT3/FT3 16.9/3.3 = 5.12.

I have an almost intact thyroid (just 1 tiny nodule too small to even biopsy). I just inserted my own values (from almost a year ago)—using the same 2 types of units as Deb did, and came up with the following:
FT3/RT3 ratio = 7.2
RT3/FT3 ratio = 13.89 or 139!!! if converted as you suggest.
I assume I’m missing something—should I be worried about these results? I had put them on the back burner and then forgot about them. My endocrinologist checks only T4 and TSH which of course are generally "normal" since the range is gigantic.

Thanks, as always,
Teri

[tex]

Teri,

I'm not sure I follow you. But units have to be consistent in mathematics, otherwise results would be arbitrary and all of physics and engineering would be pretty much useless.

Tex

[TM]

Thanks Tex,
I understand the need for maintaining consistency, but my point (obviously not clearly made) was that the ratio on the first site: FT3/RT3 works out to 19.5, whether pg/mL is entered on line 1 and ng/dL on line 2, or whether as you suggest, ng/dL should be converted and pg/mL entered on both lines.

So it seemed logical to just turn the equation upside down to make the reverse calculation: RT3/FT3. Especially in light of the warning for the need to add a decimal point if pg/mL is used on both lines of the equation. That’s where I got hung up. Myers references the 10:1 ratio, but doesn’t specifically indicate which units she’s using and I shudder to think my ratio could be that far out of range at 139 without the extra decimal.

Teri

[tex]

Teri,

I suspect you're getting bogged down in the units. If you're going to use the built-in calculator on the stopthemadness website, note that it clearly shows international units, pmol/L for both parameters.

so FT3 at 3.3 pg/mL = 5.07 pmol/L

and RT3 at 16.9 ng/dL = 259.7 pmol/L

so Rt3/FT3 = 51.2

If you ignore the units, it's possible to get 19.5 — but you can't ignore the units if you want to get accurate results.

Tex

[TM]

Thanks Tex,
Finally got it! Sometimes it takes multiple efforts to burn through my brain fog. Guess I really wanted to hang onto the extra decimal to lower my ratio from 139 to 13.9, so I misread it repeatedly. I had no idea that my FT3 and RT3 were so out of whack.
Teri

[tex]

I know what you mean. When I read something incorrectly, I'll keep making the same mistake virtually every time that I go over it. Human nature I guess. We tend to see what we want to see.

Tex