Research
Hormonal
Total testosterone levels remain relatively stable until approximately age 55 in healthy nonobese men, after which they decline rapidly, while free testosterone declines linearly from a younger age.
For healthy men, Total Testosterone stays stable until about 55. If you are younger, low Total T might not be 'just aging.' However, Free Testosterone starts dropping earlier, so symptoms may appear before Total T drops significantly.
StrongSupportsVERY_HIGH confidence
In our nonobese men, aged 25-100 yr, serum FT levels decreased approximately log linearly (1.2%/yr) with age. Total T levels, however, stayed relatively stable until age 55 yr and decreased afterward at a rate of 20.85%/yr.
Why this rating
Large sample size (n=250) covering a wide age range (25-100 years).
Source
Influence of some biological indexes on sex hormone-binding globulin and androgen levels in aging or obese males.
A. Vermeulen et al. · The Journal of Clinical Endocrinology & Metabolism · 1996
DOI 10.1210/jcem.81.5.8626841
cross_sectional · n=308Cited 442×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- In aging and obese men, elevated sex hormone-binding globulin (SHBG) levels are primarily driven by low growth hormone (GH) and insulin-like growth factor 1 (IGF-1) levels, rather than by hyperinsulinism.Good
- Obesity and high insulin levels are inversely correlated with Total Testosterone and SHBG levels, but weight loss increases SHBG even if insulin remains elevated.Good
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