The Study
THE THYROID FUNCTION IN YOUNG MEN DURING PROLONGED EXERCISE AND THE EFFECT OF ENERGY AND SLEEP DEPRIVATION
This study watched how thyroid hormones changed in soldiers during a tough training camp. It saw that when they exercised a lot and didn't eat enough, their hormone levels shifted—but it didn't test each factor alone, so we can't say for sure what caused the changes. It's like noticing your phone battery drains faster when you play games and use GPS at the same time—you know something's using power, but you don't know which one is the main culprit.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
When you exercise a lot and don't eat enough, your body switches off some of your thyroid hormones to save energy.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 538 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this is a natural survival response: your body slows metabolism to conserve energy during extreme stress like marathon training or famine.
- 2T3 (active hormone) went down, rT3 (inactive hormone) went up, and they changed together with a 0.6 correlation.
- 3TSH (brain signal to thyroid) dropped fast and stayed low.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Clinical Endocrinology
Year
1984
Authors
P. Opstad, D. Falch, O. Øktedalen, F. Fonnum, R. Wergeland
Related Content
Claims (6)
When the body experiences low energy availability or extreme stress, it converts more thyroxine into reverse T3, which lowers the metabolic rate.
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.
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.
When people get less sleep but also exercise and eat fewer calories, their thyroid hormone levels do not change significantly compared to people who get slightly more sleep under the same diet and exercise conditions.
During five days of intense exercise, reduced calorie intake, and sleep loss, thyroid-stimulating hormone levels drop quickly on the first day and stay low, reflecting reduced activity in the brain's regulation of thyroid function.
In young men who exercise intensely for long periods while consuming insufficient calories, levels of reverse T3 rise and levels of active T3 fall, with a strong statistical relationship between these changes, reflecting a metabolic shift toward thyroid hormone inactivation.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.