The Study
Serum IGF-1 and IGFBP-3 levels in healthy Korean men aged 19–40 years: a cross-sectional analysis of reference ranges and seasonal variation
This study looked at how much of two body chemicals (IGF-1 and IGFBP-3) healthy young Korean men had at different times of year. It found that the levels changed with the seasons — like more in winter or autumn — but it didn’t test why. So we know they’re linked, but we don’t know if winter weather makes the chemicals go up or if something else (like diet or sunlight) is the real reason.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Your body makes two important growth proteins, IGF-1 and IGFBP-3, and their levels go up and down like tides — not because you're sick, but because of the weather.
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 544 / 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 — using one-size-fits-all blood test ranges can make healthy young men look abnormal just because they had blood drawn in autumn or spring.
- 2IGF-1 is highest in winter (237 ng/mL) and lowest in autumn (168 ng/mL); IGFBP-3 is highest in autumn (2,901 ng/mL) and lowest in winter (1,563 ng/mL).
- 3IGF-1 drops 20% from age 19 to 40; IGFBP-3 stays the same.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Translational and Clinical Pharmacology
Year
2025
Authors
Soo-Min Jung, S. Lee, Hyoeun Lee, Eun Na Kim, K. Bae
Related Content
Claims (5)
Doctors use average blood test numbers to decide what's 'normal,' but those averages include sick people, so healthy people might be told they're unhealthy—and real health problems might be missed.
In young Korean men, a protein in the blood called IGFBP-3 goes up in the fall and drops in the winter, and it seems to rise when it’s warmer outside — which is the opposite of how another related protein, IGF-1, behaves.
When it's hotter or colder outside on the day someone gives a blood sample, their body's IGF-1 and IGFBP-3 levels tend to change in predictable ways — suggesting that the weather might be one reason these health markers go up and down with the seasons.
In young Korean men, the level of a growth-related hormone in the blood tends to be higher during winter and spring than in autumn, and this might be linked to changes in the weather.
For healthy Korean men between 19 and 40, one standard range works for IGFBP-3 blood levels, but IGF-1 levels change as you get older, so you need different ranges for different ages.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.