Longitudinal effects of aging on serum total and free testosterone levels in healthy men
Harman et al. measured testosterone and SHBG in stored serum from 890 men followed for decades in the Baltimore Longitudinal Study of Aging. Because the same men were sampled repeatedly, the study could separate true ageing from illness, medication and other age-related factors — and it is the classic description of how free, bioavailable testosterone falls faster than total testosterone as SHBG climbs.
Focus
Ageing versus cohort decline
Published finding
0.124 nmol/L
Source
10.1210/jcem.86.2.7219
Record
Ref 11
Structured abstract
Method
Harman et al. measured testosterone and SHBG in stored serum from 890 men followed for decades in the Baltimore Longitudinal Study of Aging. Because the same men were sampled repeatedly, the study could separate true ageing from illness, medication and other age-related factors — and it is the classic description of how free, bioavailable testosterone falls faster than total testosterone as SHBG climbs.
Result
Total testosterone declined on average 0.124 nmol/L per year, independent of health status. The free testosterone index declined in parallel and more steeply in relative terms, because SHBG rises with age. Hypogonadal total testosterone was present in roughly 20% of men over 60, 30% over 70 and 50% over 80. Using free testosterone criteria, an even larger share of older men fell below the cut-off.
What to take with you
The same men, sampled for decades: total T dropped 0.124 nmol/L per year, and free T dropped steeper still as SHBG rose.
Why it matters
In the same men followed for decades, total T fell 0.124 nmol/L per year — and free T fell steeper still as SHBG rose.
Study frame
Ageing versus cohort decline
Harman et al. measured testosterone and SHBG in stored serum from 890 men followed for decades in the Baltimore Longitudinal Study of Aging. Because the same men were sampled repeatedly, the study could separate true ageing from illness, medication and other age-related factors — and it is the classic description of how free, bioavailable testosterone falls faster than total testosterone as SHBG climbs.
Finding
Total testosterone declined on average 0.124 nmol/L per year, independent of health status.
Contrast
The free testosterone index declined in parallel and more steeply in relative terms, because SHBG rises with age.
Context
Hypogonadal total testosterone was present in roughly 20% of men over 60, 30% over 70 and 50% over 80.
DOI
10.1210/jcem.86.2.7219
Category
Ageing versus cohort decline
Findings listed
4
Type
As published
What to take from the numbers
Boxes below use only wording already in the published summary for this study.
Reported finding
0.124 nmol/L
Total testosterone declined on average 0.124 nmol/L per year, independent of health status.
Reported finding
2
The free testosterone index declined in parallel and more steeply in relative terms, because SHBG rises with age.
Reported finding
20%
Hypogonadal total testosterone was present in roughly 20% of men over 60, 30% over 70 and 50% over 80.
An observational longitudinal cohort with immunoassay measurements; it describes decline over time, not what treatment achieves.
Why it matters when reading your own result
Pulled from the study's own findings.
Total testosterone declined on average 0.124 nmol/L per year, independent of health status.
Ageing versus cohort decline
The free testosterone index declined in parallel and more steeply in relative terms, because SHBG rises with age.
Ageing versus cohort decline
Hypogonadal total testosterone was present in roughly 20% of men over 60, 30% over 70 and 50% over 80.
Ageing versus cohort decline
Clinical reading
How to use this page
Harman et al. measured testosterone and SHBG in stored serum from 890 men followed for decades in the Baltimore Longitudinal Study of Aging. Because the same men were sampled repeatedly, the study could separate true ageing from illness, medication and other age-related factors — and it is the classic description of how free, bioavailable testosterone falls faster than total testosterone as SHBG climbs.
Related studies in this library
Journal of Clinical Endocrinology & Metabolism · 2007
A population-level decline in serum testosterone levels in American men
European Journal of Endocrinology 168: 227–233 · 2013
A cohort effect on serum testosterone levels in Finnish men
Journal of Clinical Endocrinology & Metabolism 92: 4696–4705 · 2007
Secular decline in male testosterone and SHBG serum levels in Danish population surveys
Your own numbers
Measure before you decide what this page means for you.
The figures here describe men who were actually measured.
- Total testosterone and SHBG
- Symptoms written down
- Haematocrit as a safety baseline
- Repeat labs before any protocol change