Do adrenal DHEA-S and pregnenolone supply substrates for androgen production in postmenopausal women?

In the context of postmenopausal physiology, adrenal-derived steroid precursors play a critical role in maintaining androgenic activity. As ovarian function declines, the adrenal glands become the primary source of the substrates necessary for sex steroid synthesis.

Adrenal origin and biosynthetic pathway

The adrenal cortex is the dominant site for the production of pregnenolone and dehydroepiandrosterone sulfate (DHEA-S).

• Pregnenolone synthesis: Within the adrenal mitochondria, cholesterol is converted to pregnenolone via the enzyme CYP11A1 (P450scc), a process primarily regulated by adrenocorticotropic hormone (ACTH).
• Conversion to DHEA-S: Pregnenolone is subsequently converted to DHEA through the actions of the CYP17A1 enzyme. In the adrenal zona reticularis, DHEA is rapidly sulfated by the enzyme SULT2A1 to form DHEA-S.
• Adrenal dominance: In women aged 60 and older, the adrenal glands contribute approximately 90% to 95% of circulating DHEA-S. While these levels generally decline with age, they remain the most abundant circulating steroid precursors in the body.

Contribution to downstream androgens

DHEA-S and pregnenolone serve as the foundational building blocks for active androgens through a process known as intracrinology, where conversion occurs within peripheral tissues.

• The reservoir effect: DHEA-S acts as a large molecular reservoir. In peripheral tissues such as the skin, adipose tissue, and bone, the enzyme steroid sulfatase converts DHEA-S back into DHEA.
• Androgen synthesis: DHEA is then converted into androstenedione via 3β-hydroxysteroid dehydrogenase (3β-HSD) and subsequently into testosterone and dihydrotestosterone (DHT) by 17β-hydroxysteroid dehydrogenase (17β-HSD) and 5α-reductase.
• Relative contribution: Research indicates that this adrenal-to-androgen pathway accounts for approximately 66% of total androgen production in women. Longitudinal data demonstrate that fluctuations in adrenal precursors like DHEA-S are closely mirrored by changes in serum testosterone, confirming their functional role as substrates.

Mechanistic significance

The ability of the body to synthesize androgens from adrenal precursors is vital for maintaining physiological functions in postmenopausal women, including bone density and muscle mass.

• Intracrine regulation: Unlike systemic hormones, these androgens are often synthesized and exert their effects locally within the same cells, minimizing systemic exposure while maintaining tissue-specific androgenic signaling.
• Precursor availability: Because pregnenolone is the proximal precursor for all downstream steroids, its availability (driven by cholesterol transport via the StAR protein) fundamentally limits the total potential for adrenal androgen production.

Bottom line

DHEA-S and pregnenolone are the primary adrenal precursors that sustain androgen levels in postmenopausal women. Through peripheral conversion, these steroids provide a significant majority of the body's testosterone and androstenedione, serving as a critical endocrine buffer following the cessation of ovarian function.