Does aging in men raise SHBG and lower DHEA-S despite preserved total testosterone?

Healthy endocrine aging in men involves a distinct biochemical shift that alters androgen dynamics independently of total circulating hormone levels. This process is driven by concurrent changes in liver and adrenal gland function.

Clinical evidence and hormonal shifts

• Reciprocal hormonal changes: Longitudinal data show that circulating sex hormone-binding globulin (SHBG) increases by 1% to 3% annually in aging men. Conversely, dehydroepiandrosterone sulfate (DHEA-S) declines by 1% to 4% per year, resulting in an 80% to 90% reduction by late life compared to youthful peaks.
• Masked deficiency: Because conventional laboratory assessments often focus solely on total testosterone, these shifts can mask tissue-level androgen deficiency. Patients frequently present with clinical symptoms of hypogonadism—including fatigue, muscle mass loss, and decreased libido—despite maintaining "normal" total testosterone levels.

Mechanistic explanations

• SHBG sequestration: Age-related increases in hepatic SHBG synthesis, partly regulated by transcription factors like HNF-4alpha and PPAR-gamma, lead to elevated circulating SHBG. This protein tightly binds circulating testosterone, lowering the free, bioavailable fraction capable of activating target tissue receptors.
• Intracrine depletion: Progressive cellular involution of the adrenal zona reticularis reduces circulating DHEA-S. This depletes the essential precursor required for peripheral intracrine androgen synthesis. This localized pathway, mediated by steroid sulfatase in target tissues like skin and adipose, normally accounts for 30% to 50% of total androgen synthesis in men.

Bottom line

• Key takeaway: Aging reduces bioavailable androgen activity through increased hepatic SHBG binding and diminished adrenal DHEA-S intracrine precursor availability, meaning functional androgen deficiency can manifest even when total testosterone is fully preserved.