The Claim

The ratio of free thyroxine (FT4) to total thyroxine (T4) remains tightly correlated (r = 0.9) during prolonged physical stress, indicating that changes in thyroid hormone binding proteins do not significantly alter the biologically active fraction of thyroid hormone.

Source: THE THYROID FUNCTION IN YOUNG MEN DURING PROLONGED EXERCISE AND THE EFFECT OF ENERGY AND SLEEP DEPRIVATION

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
38score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Correlation
1 study reviewed
In plain English

During prolonged physical stress, the proportion of free thyroxine relative to total thyroxine stays consistently high, showing that changes in binding proteins do not reduce the amount of active hormone available to tissues.

See the scientific wording

The ratio of free thyroxine (FT4) to total thyroxine (T4) remains tightly correlated (r = 0.9) during prolonged physical stress, indicating that changes in thyroid hormone binding proteins (e.g., TBG) do not significantly alter the biologically active fraction of hormone.

Why this might work

When the body is under long-term physical stress, it reduces the amount of active thyroid hormone in tissues by converting more of it into an inactive form, but the proportion of hormone that is free and able to act on cells stays exactly the same as the total hormone level changes. This happens because the proteins that carry thyroid hormone in the blood adjust their levels in sync with how much hormone is made, so the free part always matches the total part.

Verified mechanismbased on 1 study

What the research says

1 study

  1. Study: THE THYROID FUNCTION IN YOUNG MEN DURING PROLONGED EXERCISE AND THE EFFECT OF ENERGY AND SLEEP DEPRIVATION

    When soldiers went through intense training without enough food, their total thyroid hormone went up and down, but the part that actually works in the body went up and down at the same rate — meaning the carrier proteins didn’t block or change how much active hormone was available.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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