The Claim
Prolonged physical exercise combined with calorie restriction in young men induces a biphasic change in thyroid hormone levels, characterized by an initial increase in T4, FT4, T3, and rT3 secretion followed by a decline in thyroid hormone production and a shift in peripheral deiodination from T3 to rT3 production.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
In young men, sustained physical exercise with reduced calorie intake causes thyroid hormone levels to first rise and then fall, while the body's conversion of hormones shifts from producing T3 to producing rT3.
See the scientific wording
Prolonged physical exercise combined with calorie restriction in young men leads to a biphasic change in thyroid hormone levels: an initial increase in T4, FT4, T3, and rT3 secretion followed by a decline in thyroid hormone production and a shift in peripheral deiodination from T3 to rT3 production, indicating a metabolic adaptation to sustained energy deficit.
When a person exercises intensely for many days without enough food, the body first makes more thyroid hormones to meet the high energy demand. After a few days, it stops making as much of the active hormone and starts making an inactive version instead, slowing down metabolism to save energy.
What the research says
1 studyWhen young men do lots of hard exercise without enough food, their thyroid hormones first go up, then drop, and their body starts making a less active version of the hormone instead of the active one—this helps them save energy during tough times.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.