The Study
Developmental regulation of fetal mitochondrial respiratory function towards term: the role of glucocorticoid and thyroid hormones
This study is like a summary of other scientists' experiments with baby sheep and rats — it tells you what they noticed, like 'when hormone levels go up, mitochondria change.' But it didn't do any experiments itself, so it can't prove that one thing causes another — it just says 'maybe this happens.'
Analysis score
Maximum 5 for a narrative review.
Where the score came from
Before birth, a baby's body builds tiny energy factories (mitochondria) in muscles and organs, using hormones like cortisol and T3 as instructions. These factories stay mostly off until birth, then turn on full power to help the baby breathe, stay warm, and move.
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 51 / 100
Quality score
Systematic reviews and meta-analyses of cohort studies. They sit above a single cohort study but below a single randomized trial, because the underlying evidence is still observational.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes—this preparation is critical.
- 2Without it, newborns struggle to survive outside the womb, and later in life, they may develop diabetes or obesity.
- 3When hormones rise normally, mitochondria multiply and get ready.
- 4If hormones are too low (e.g., thyroid removed), mitochondria don't grow well.
- 5If cortisol is given too long, mitochondria become weaker.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The Journal of Endocrinology
Year
2025
Authors
AL Fowden, KL Davies, Ej Camm, A. Forhead, AJ Murray
Related Content
Claims (10)
Triiodothyronine (T3) increases the rate at which cells produce ATP through mitochondrial respiration, oxygen use, and glucose breakdown, resulting in less metabolic byproduct formation.
Removing the adrenal glands from fetal sheep decreases mitochondrial content and energy production in skeletal muscle by term, while administering cortisol before term increases these parameters, showing that glucocorticoid exposure directly influences fetal mitochondrial development.
During late pregnancy in mice and rats, placental mitochondria in female fetuses adjust their energy production based on fetal weight, while male fetuses do not show this adjustment, and sex hormones may influence this difference.
In fetal sheep, low thyroid hormone levels cause a decrease in mitochondrial density, reduced activity of the cellular energy production system, and lower capacity for fat burning in muscle and fat tissues, and this effect occurs regardless of glucocorticoid levels.
Extended exposure to stress hormones in pregnant sheep and rodents is linked to lower mitochondrial energy production and reduced creation of new mitochondria in fetal tissues, compared to brief exposure.
During late pregnancy in sheep fetuses, rising levels of glucocorticoid and thyroid hormones coincide with higher mitochondrial density, more electron transport chain proteins, and greater energy production capacity in skeletal muscle, liver, heart, and brain tissues.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.