Androstenedione, Testosterone, and DHT

1. Background

Androgen assessment in routine practice is commonly a single testosterone measurement. Yet testosterone is a midpoint in a metabolic sequence: a weak precursor feeds it, a more potent product derives from it, and a parallel route converts both to estrogens.

Reading only the midpoint discards where the androgen came from and what it becomes.

This review makes the case for measuring the three principal androgens together — androstenedione, testosterone and DHT — and interpreting the ratios that encode the pathway and its enzymes.

2. One pathway, three androgens

Androstenedione, a weak androgen produced by adrenal and gonadal tissue, is converted to testosterone by 17β-hydroxysteroid dehydrogenase; testosterone is reduced to dihydrotestosterone by 5α-reductase in target tissues; and both can exit the androgen pathway to estrogens via aromatase.

DHT is the most potent androgen — the highest-affinity androgen-receptor ligand, and non-aromatisable — and much of its action is intracrine, generated within skin, hair follicle and prostate.^3,10

The corollary is that the three analytes report different things:

• Androstenedione reports precursor supply
• Testosterone reports circulating androgen
• DHT reports potent, tissue-level androgen activation

3. The ratios encode enzyme activity and source

Because each step is catalysed by a distinct enzyme, the ratios between the three analytes are themselves informative:

• T:A4 reflects 17β-HSD conversion of precursor to active androgen
• DHT:T reflects 5α-reductase activity
• A disproportionately high androstenedione points upstream — toward an adrenal or ovarian source, or an enzymatic block

In polycystic ovary syndrome, simultaneous LC-MS/MS profiling shows elevated testosterone and androstenedione together with an altered product-to-precursor ratio, localising the androgen excess to the ovary rather than the adrenal.²

A single analyte cannot separate these possibilities; the pathway can.

4. Metabolic patterns imposed by enzyme inhibitors

Two common therapies rewrite the pathway in predictable, measurable ways.

5α-reductase inhibitors (finasteride, dutasteride) block the conversion of testosterone to DHT: serum and scalp DHT fall — dutasteride lowering DHT more completely than finasteride, dose-dependently — while testosterone rises, inverting the DHT:T ratio.⁴ Finasteride reduces circulating DHT by roughly 70%, and prostatic DHT still further.⁵

Aromatase inhibitors block the conversion of testosterone to estradiol, and androstenedione to estrone: estrogens fall and androgens accumulate, so testosterone rises as its estrogen exit is closed.^7,8

In each case it is measurement of the pathway — not of a single analyte — that makes the shift legible.

5. Applications favouring measurement of all three

5.1 Hyperandrogenism and PCOS

Total and free testosterone are the first-line laboratory tests for biochemical hyperandrogenism, with androstenedione and DHEA-S adding source information when testosterone is not elevated; the 2023 International PCOS Guideline analysis supports this tiered approach and recommends LC-MS/MS for accuracy.¹ Adding androstenedione and reading the product-to-precursor ratio helps distinguish ovarian from adrenal excess.²

5.2 Congenital adrenal hyperplasia

In 21-hydroxylase deficiency, androstenedione — together with 17-hydroxyprogesterone — is a core marker of androgen control, monitored alongside testosterone.⁶

5.3 Androgen-dependent skin and hair conditions

DHT and 5α-reductase drive androgenetic alopecia, hirsutism and acne.³ Measuring DHT and the DHT:T ratio characterises peripheral androgen activation.

5.4 Therapy and disease monitoring

The panel tracks the effects of 5α-reductase and aromatase inhibitors, and in prostate cancer it exposes what a single value hides: under androgen deprivation, DHT can persist through intracrine and backdoor synthesis, and androstenedione becomes associated with testosterone in castration-resistant disease — patterns visible only when precursors and products are measured together.^9,10

6. Analytical considerations

Androgens span a wide dynamic range and are frequently low — in women, in children, and under pharmacologic suppression — where direct immunoassays are unreliable, particularly for androstenedione and DHT; radioimmunoassay overestimates androstenedione relative to mass spectrometry.²

The 2023 International PCOS Guideline analysis explicitly recommends LC-MS/MS for androgen measurement given its accuracy, and validated panels quantify androstenedione, testosterone and DHT from a single specimen.¹

Where the DHT:T ratio can and cannot be computed

The ratio arguments above depend on a quantifiable DHT, and that is a real constraint rather than a theoretical one.

Clinicore reports DHT from 10.125 ng/dL. That covers most of the female reference interval and the elevated concentrations characterising androgen excess — hirsutism, PCOS, androgenetic alopecia, suspected 5α-reductase overactivity. Concentrations below the limit are reported as less than the limit.

Two of the applications in this review fall outside it. Monitoring DHT suppression during 5α-reductase inhibitor therapy drives DHT well below the reportable limit — that is the therapy working — and a numeric DHT:T ratio cannot be computed at suppressed concentrations. Neither can it be computed at low female concentrations below the limit.

The pathway argument holds. The specific numeric ratio does not, at those concentrations, on this assay. See the DHT analyte page for the full statement.

Table 1. The three androgens at a glance

Property	Androstenedione	Testosterone and DHT
Role	Weak precursor androgen	T: principal androgen · DHT: most potent (highest AR affinity)
Principal source	Adrenal and gonadal	T: testis/ovary and peripheral · DHT: 5α-reduction in target tissue
Key enzyme step	17β-HSD → T; aromatase → estrone	5α-reductase T→DHT; aromatase T→estradiol
Reports	Precursor supply and source	Circulating androgen (T) and potent tissue activation (DHT)
With aromatase inhibitor	Rises (estrogen exit blocked)	Testosterone rises; estrogens fall
With 5α-reductase inhibitor	—	DHT falls sharply; testosterone rises
Preferred assay	LC-MS/MS (immunoassay unreliable)	LC-MS/MS

7. Conclusions and recommendations

Androgen status should not be read from a single point. Measure androstenedione, testosterone and DHT together and interpret the ratios: T:A4 for precursor conversion, DHT:T for 5α-reductase activity, and a disproportionate precursor for source.

Read this way the panel localises androgen excess, exposes enzyme activity, and makes the effects of 5α-reductase and aromatase inhibitors legible — with an assay accurate across the ranges where these questions are actually decided, and with the DHT reporting limit in §6 understood.