FT3, FT4 and cardiovascular correlation

[diogenes]

This new paper uses a very large public trial panel of patients to uncover what the levels of FT4 and FT3 may correlate with future risks of cardiac problems. This examines the subgroup of control patients with no thyroidal problems. Here, title and abstract in full. FT4/FT3 ratios are quite stable in euthyroids so the ratio does correlate with the entities compared. It again indicates that high-normal FT4 has some correlation with later cardiovascular events. It seems as if poorer conversion leading to a high FT4/FT3 ratio requires some actions when discovered. I've turned the ratio on its head because I'm more used to this.

FT3/FT4 ratio is correlated with all-cause mortality, cardiovascular mortality, and cardiovascular disease risk: NHANES 2007-2012

Xueyan Lang1,2†, Yilan Li1,2†, Dandan Zhang1,2, Yuheng Zhang1, Nilian Wu1 and Yao Zhang1,2*

Background: Thyroid hormones play a vital role in maintaining the homeostasis of the cardiovascular system. The FT3/FT4 ratio can be used to evaluate the rate of T4-to-T3 conversion, reflecting the peripheral sensitivity of thyroid hormones. There is no study to investigate its relationship with death and cardiovascular disease (CVD) in the general population.Methods: This retrospective cohort study involved 8,018 participants with measured thyroid function and no prior thyroid disease who participated in the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2012. Mortality status was determined by routine follow-up using the National Death Index through December 31, 2015.

Results: During a median of 87 months of follow-up, we observed 699 all-cause deaths, including 116 cardiovascular deaths. In multivariate adjusted models, higher free thyroxine (FT4) was linked to increased all-cause mortality (HR, 1.15 per SD; 95% CI, 1.09-1.22), cardiovascular mortality (HR, 1.18 per SD; 95% CI, 1.01-1.39), and CVD risk (HR, 1.17 per SD; 95% CI, 1.08-1.27). Higher free triiodothyronine (FT3) was linked to decreased all-cause mortality (HR 0.81 per SD; 95% CI, 0.70-0.93). Higher FT3/FT4 ratio was linked to decreased all-cause mortality (HR, 0.77 per SD; 95% CI, 0.69-0.85), cardiovascular mortality (HR, 0.79 per SD; 95% CI, 0.62-1.00), and CVD risk (HR, 0.82 per SD; 95% CI, 0.74-0.92). The FT3/FT4 ratio stratified findings were broadly consistent with the overall results.

Conclusions: FT3, FT4, and the FT3/FT4 ratio were all independent predictors of all-cause death. FT4 and the FT3/FT4 ratio, BUT NOT FT3 (my emphasis), were independent predictors of cardiovascular mortality and CVD risk. Along with FT3 and FT4, we should pay equal attention to the FT3/FT4 ratio in the general population.

[Tythrop]

Sorry Im a bit of a bimbo but does this suggest that if you have low 3 and low 4 you are more likely to have cv probs or less ? Are the high t3 and 4 the Hyperactive people ?

What if you have OK T4 but low t3 ( conversion issues?

What if you have downregulation issues...ie tsh stuck so t4 stuck on low and therefore t3 low ?

Forgive me for asking

[diogenes Remembering in reply to Tythrop]

If there is no relationship between cardiac problems and FT3, but there is with FT4, then the ratio will indicate statistically probable outcomes. Note this is nothing to do with patients on therapy and the outlook for them will likely be quite different. People on T4 or T4/T3 or whatever should not read into this something relevant to them.

[TaraJR]

frontiersin.org/articles/10...

[nellie237]

"Along with FT3 and FT4, we should pay equal attention to the FT3/FT4 ratio in the general population."

It would be nice if they paid attention to those of us with thyroid disease (and CVD) too. 🙂

[diogenes Remembering in reply to nellie237]

The great thing here is the suggestion which I have banged on about for ages - ever since I came on this forum - in health, FT4 and FT3 should be measured say at 10 years intervals to show roughly where in the reference ranges the patient's results lie - it needn't be any more exact than "you're in the bottom third, the middle third or the top third of FT3 ranges and your FT4/FT3 ratio is ***. The higher the ratio the bigger the suspicion that if you do eventually become ill thyroidally, you might not handle T4 only well. At least we can check out if you can handle T4 therapy alone even before beginning therapy, having this prior knowledge.

[Litatamon in reply to diogenes]

Baselines are highly underrated, that is for sure.

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Off topic a bit, but what is the appropriate range for t4 to t3 conversion with treatment? Should they be equal in range? Or no?

(I am around 70% for t4 & 50% for t3 - levothyroxine monotherapy after a thyroidectomy. But this is from a very high dose, 225 mcg)

[diogenes Remembering in reply to Litatamon]

If on T4 only, you wouldn't want the FT4/FT3 ratio much above 4/1 and at 4.5/1 should be thinking of T3 supplementation

[Jumbelina]

Thank you for posting this very large, informative study and for your very useful comments on it.