Research
Hormonal
Low energy availability causes a 'sick euthyroid' profile with decreased T3 and increased reverse T3, reducing energy expenditure as an adaptive response.
Low energy intake can lower your T3 levels as a way to conserve energy. This is a normal adaptation, not necessarily a thyroid disease. Focus on eating enough to support your activity level, which should normalize your thyroid hormones.
GoodSupportsHIGH confidence
In response to periods of low EA, the hypothalamic-pituitary-thyroid axis adapts in order to reduce energy expenditure and a 'sick euthyroid' profile is often noted (Misra & Klibanski, 2014).
Why this rating
Supported by multiple studies showing decreased T3 in low EA states.
Source
Endocrine Effects of Relative Energy Deficiency in Sport
Kirsty J. Elliott‐Sale et al. · International Journal of Sport Nutrition and Exercise Metabolism · 2018
DOI 10.1123/ijsnem.2018-0127
narrative_reviewCited 219×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Low energy availability (EA <30 kcal/kg FFM/day) causes functional hypothalamic amenorrhea (FHA) in female athletes through suppressed GnRH pulsatility, leading to decreased estradiol and progesterone.Good
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- Low energy availability suppresses leptin levels and elevates ghrelin and peptide YY (PYY), disrupting appetite regulation and contributing to the maintenance of low energy states.Good
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