Cross SectionalHumann = 27,328 (7,940 with bioavailable testosterone data)2022
Seasonal Variation of Testosterone Levels in a Large Cohort of Men.
Plain-language summary
This study set out to see whether testosterone in men varies with the season, independently of age, weight and existing illness. It used the medical records of 27,328 Israeli men aged 20 to 70 who had had testosterone measured, including 7,940 with the bioavailable form, the part not locked to proteins and available to the body. Testosterone was highest in August to October and lowest in March, and the pattern held after accounting for age, weight, smoking and conditions such as diabetes and heart disease. Another study in this library asks the same question in a separate Italian dataset, so the two are independent of each other.
Key findings
- Total and bioavailable testosterone were highest from August to October and lowest in March.
- Testosterone fell with age and with higher body weight, and was lower in men with diabetes, high blood pressure, high cholesterol or heart disease.
- The month of the blood test was linked to testosterone even after the other factors were accounted for.
How to analyze the study yourself
- Study type
- Cross-sectional studies capture data at one point in time, so they can spot patterns but cannot prove cause and effect or track changes over time in the same individuals.
- Population
- Israeli men aged 20-70 with testosterone measurements in their medical records.
- Funding
- Not reported
- Takeaway
- This study found that testosterone levels in men peak in late summer and early fall and hit their lowest point in March. If you're tracking your testosterone, it may be worth noting the time of year when interpreting your results.