The Study
Body weight and waist circumference are differentially associated with the response to L-thyroxine treatment in primary hypothyroidism
This study looked at 15 people with thyroid problems and noticed that when their thyroid hormone levels changed, their waist size and weight also changed — but it didn't prove that one caused the other. It's like noticing that ice cream sales go up when people wear shorts — they happen together, but one doesn't cause the other.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
When people with underactive thyroids start taking thyroid medicine, some gain weight and some lose belly fat — and both can be signs their body is healing.
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 546 / 100
Quality score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Gaining weight here may mean more muscle or energy, not just fat — and it came with better mood and energy.
- 2Losing belly fat means better heart health, even if total weight didn't change.
- 3Weight gain linked to higher orexin (r=0.78) and better mood (r=0.72).
- 4Belly fat loss linked to higher brain thyroid hormone (r=-0.71).
- 5Weight and belly fat changes didn't match up.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of Clinical & Translational Endocrinology
Year
2026
Authors
A. Funkquist, Stefan Sjöberg, Henrik Zetterberg, Stefan Bergman, Josefine Rosvall, P. Bjellerup, Johan Svensson
Related Content
Claims (6)
In people newly diagnosed with hypothyroidism taking L-thyroxine, changes in waist size do not relate to changes in body weight, showing that these two measurements track different metabolic changes.
When thyroid hormone levels are low, the body's metabolic rate decreases, leading to less fat burning, weight gain, constipation, and fatigue.
In people newly diagnosed with hypothyroidism, a greater increase in cerebrospinal fluid free thyroxine levels after six months of L-thyroxine treatment is associated with a larger reduction in waist circumference, even when total body weight does not change.
In people newly diagnosed with hypothyroidism, higher levels of orexin in the cerebrospinal fluid before treatment are associated with greater weight gain during six months of L-thyroxine therapy, and this weight gain is linked to improved quality of life.
Among people newly diagnosed with hypothyroidism, those who gain weight during six months of L-thyroxine treatment tend to report greater improvements in physical and mental well-being.
In people newly diagnosed with hypothyroidism, greater reductions in LDL cholesterol after six months of L-thyroxine treatment are linked to higher levels of free thyroxine in the cerebrospinal fluid, regardless of thyroid hormone levels in the blood.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.