Why your blood test numbers change with the seasons
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
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
IGF-1 and IGFBP-3 move in opposite directions with temperature and season.
Most people assume all hormones rise or fall together with environmental cues. This study shows they’re opposites—IGF-1 loves cold, IGFBP-3 loves heat.
Practical Takeaways
If you're getting a blood test for IGF-1, ask if the lab uses age- and season-adjusted reference ranges—or get tested in winter for a more 'typical' result.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
IGF-1 and IGFBP-3 move in opposite directions with temperature and season.
Most people assume all hormones rise or fall together with environmental cues. This study shows they’re opposites—IGF-1 loves cold, IGFBP-3 loves heat.
Practical Takeaways
If you're getting a blood test for IGF-1, ask if the lab uses age- and season-adjusted reference ranges—or get tested in winter for a more 'typical' result.
Publication
Journal
Translational and Clinical Pharmacology
Year
2025
Authors
Soo-Min Jung, S. Lee, Hyoeun Lee, Eun Na Kim, K. Bae
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Claims (5)
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.
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, 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.