Is DHEA-S produced mainly by the adrenal cortex and converted into testosterone in peripheral tissues?

Dehydroepiandrosterone sulfate (DHEA-S) is the most abundant circulating steroid hormone in the human body. In women, it serves as a critical reservoir for the synthesis of active sex steroids, providing a stable source of androgens that can be activated locally within specific tissues.

Adrenal production and enzymatic synthesis

The adrenal cortex is the primary site of DHEA-S production, specifically within the zona reticularis. While the ovaries contribute to the androgen pool, the adrenal glands are responsible for approximately 50% to 90% of circulating DHEA-S in reproductive-age women, with some estimates suggesting the adrenal contribution exceeds 95% across the general population.

• Molecular Pathway: Synthesis begins with the conversion of pregnenolone into DHEA via the enzyme CYP17A1, which possesses both 17α-hydroxylase and 17,20-lyase activities.
• Sulfation Process: Unlike the gonads, the adrenal cortex expresses high levels of the sulfotransferase enzyme SULT2A1. This enzyme rapidly converts DHEA into DHEA-S, a modification that significantly extends the hormone's half-life and allows it to reach high concentrations in the bloodstream.

Peripheral conversion to testosterone

DHEA-S acts as a "pro-hormone" that lacks intrinsic androgenic activity until it is converted into active forms in peripheral tissues—a process known as intracrinology. This mechanism allows tissues to regulate their own androgen levels independently of systemic circulation.

• Enzymatic Cascade: The conversion into testosterone requires a three-step enzymatic process:
  1. Steroid Sulfatase (STS): Removes the sulfate group from DHEA-S to regenerate DHEA.
  2. 3β-Hydroxysteroid Dehydrogenase (3β-HSD): Converts DHEA into androstenedione.
  3. 17β-Hydroxysteroid Dehydrogenase (17β-HSD/AKR1C3): Reduces androstenedione into testosterone.
• Target Tissues: This machinery is highly active in the skin (keratinocytes and sebaceous glands), adipose tissue, and skeletal muscle. In women, this peripheral pathway is a major contributor to total testosterone levels, as a significant portion of female testosterone is derived from adrenal precursors rather than direct ovarian secretion.

Bottom line

DHEA-S is primarily produced by the adrenal cortex and functions as a stable precursor that peripheral tissues—such as the skin and fat—convert into active androgens like testosterone through a specific enzymatic sequence (STS, 3β-HSD, and 17β-HSD).