Does low DHEA-S reduce sex-steroid availability in older women?

In postmenopausal women, the hormonal landscape shifts significantly as ovarian production of estrogens and androgens effectively ceases. Consequently, the body relies almost entirely on the "intracrine" system—the peripheral conversion of adrenal precursors into active sex steroids within local tissues.

Clinical evidence and sex-steroid availability

For women in their 70s, adrenal dehydroepiandrosterone sulfate (DHEA-S) is the most abundant circulating steroid and the primary raw material for hormone synthesis.

• Declining Precursor Pool: DHEA-S levels peak in the 20s and decline by approximately 2% per year. In women aged 70 and older, this reservoir is significantly depleted, directly limiting the substrate available for conversion into active hormones.
• Correlation with Active Hormones: Research involving postmenopausal cohorts (e.g., the Study of Women's Health Across the Nation) shows that circulating DHEA-S levels correlate with serum testosterone (r ≈ 0.40) and estrone. Lower levels of DHEA-S are consistently associated with reduced total androgenic and estrogenic metabolites.
• The Role of SHBG: As women age, Sex-Hormone Binding Globulin (SHBG) often increases. This protein binds to the already diminished supply of testosterone and estradiol, further reducing the "free" or bioavailable fraction of these hormones reaching the cells.

Mechanistic explanations

The conversion process occurs in peripheral tissues such as the skin, bone, adipose tissue, and brain, which express specific enzymatic machinery.

• Sulfatase Pathway: Circulating DHEA-S acts as a stable reservoir. It is converted to free DHEA by the enzyme steroid sulfatase (STS) within target tissues.
• Androgen Synthesis: Once converted to DHEA, tissues use 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-HSD to produce androstenedione, testosterone, and dihydrotestosterone (DHT).
• Estrogen Synthesis: These androgens are then converted into estrogens (estrone and estradiol) via the aromatase enzyme (CYP19A1). Because this happens locally, tissue-specific levels may be higher than what is reflected in standard blood tests.

Bottom line

In older women, DHEA-S is the essential substrate for nearly 100% of estrogens and the majority of androgens. Low DHEA-S levels significantly limit the precursor pool, leading to reduced tissue-specific availability of active sex steroids.