When people don't eat for 3 days, their active thyroid hormone (FT3) levels drop, but their overall thyroid hormone (FT4) stays the same, showing how the thyroid adapts to fasting.
Scientific Claim
During acute starvation in healthy young adults, plasma free triiodothyronine (FT3) levels decrease progressively from baseline to 72 hours, while free thyroxine (FT4) levels remain unchanged, suggesting thyroid hormone adaptation to fasting.
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The study design (cohort study) can describe associations between starvation and physiological changes. The claim uses 'decrease' and 'remain unchanged' which appropriately reflects the observed association.
Source Excerpt
“FT3 levels gradually fell (Fig. 5; time effect P < 0.001, ANOVA). FT4 levels did not change during starvation (Fig. 5).”
Evidence from Studies
Supporting Evidence (1)
The study measured thyroid hormone levels at multiple time points during starvation and found a statistically significant decline in FT3 while FT4 remained unchanged, indicating specific thyroid hormone adaptations to fasting.
The cardiovascular, metabolic and hormonal changes accompanying acute starvation in men and women