Androstenedione
The androstenedione test measures a 19-carbon steroid precursor to both testosterone and oestrone, secreted by the adrenal glands and gonads. It is used to investigate hyperandrogenism in women (PCOS, virilisation, adrenal or ovarian tumours), to diagnose and monitor congenital adrenal hyperplasia, and to evaluate adrenarche in children, interpreted alongside DHEA-S, testosterone, and…
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Biomarkers
Blood (serum)
Sample
2–4 business days
Turnaround
No
Fasting
What is the A4 test?
The Androstenedione test measures a key androgen precursor that straddles adrenal and gonadal steroidogenesis. It is ordered primarily to investigate hyperandrogenism in women, where an elevated result points to either ovarian or adrenal androgen overproduction, and to evaluate suspected enzyme defects in the steroidogenic pathway — most notably 21-hydroxylase and 3β-hydroxysteroid dehydrogenase deficiencies in congenital adrenal hyperplasia. Androstenedione rarely acts alone diagnostically: practitioners interpret it alongside DHEA-S (which is predominantly adrenal), testosterone, 17-hydroxyprogesterone (elevated in 21-hydroxylase deficiency), and clinical features to localise pathology. In women with hirsutism or oligo-ovulation, a moderately elevated androstenedione in the context of normal DHEA-S and 17-OHP suggests polycystic ovary syndrome, while a markedly elevated value or one that rises disproportionately with DHEA-S raises concern for an adrenal tumour. The test is also used in paediatric endocrinology to assess premature adrenarche and to monitor treatment of CAH.
What does the A4 test measure?
Androstenedione is a 19-carbon steroid synthesised in the adrenal cortex, gonads, and peripheral tissues. It is the immediate precursor to both testosterone (via 17β-hydroxysteroid dehydrogenase) and oestrone (via aromatase), placing it at the intersection of androgen and oestrogen biosynthesis. In men the majority arises from the adrenal glands and testicular production, while in women it is secreted roughly equally by the adrenals and ovaries, with additional peripheral conversion in adipose tissue. Androstenedione itself has weak androgenic activity but serves principally as a prohormone; its circulating concentration reflects both glandular secretion and peripheral interconversion.
Androstenedione is measured to investigate androgen excess in women (hirsutism, virilisation, and polycystic ovary syndrome), to evaluate suspected adrenal or gonadal tumours, and to assess congenital adrenal hyperplasia and premature or delayed adrenarche in children. In women elevated androstenedione may originate from the ovary (PCOS, androgen-secreting tumour) or the adrenal (non-classic CAH, Cushing syndrome, adrenal tumour), and correlation with DHEA-S, 17-hydroxyprogesterone, and stimulation testing helps localise the source. In men isolated androstenedione elevations are uncommon but may accompany adrenal enzyme defects or androgen-secreting tumours.
Why is the A4 test ordered?
- Investigation of hirsutism, acne, alopecia, or oligo-amenorrhoea in reproductive-age women when polycystic ovary syndrome or another hyperandrogenic disorder is suspected
- Evaluation of virilisation (clitoromegaly, deepening voice, male-pattern hair loss) to distinguish ovarian from adrenal androgen excess
- Work-up of suspected androgen-secreting tumour of the ovary or adrenal gland, particularly when androgen elevations are marked or progressive
- Diagnosis and monitoring of non-classic (late-onset) congenital adrenal hyperplasia, interpreted with basal and ACTH-stimulated 17-hydroxyprogesterone
- Assessment of premature adrenarche or delayed puberty in children, where androstenedione helps evaluate adrenal androgen production
- Follow-up of known CAH on glucocorticoid replacement to ensure adequate suppression of adrenal androgen synthesis
- Investigation of secondary amenorrhoea or infertility when an androgen-excess disorder is in the differential
- Evaluation of ambiguous genitalia in the newborn, as part of the steroid profile to identify enzyme defects
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Venipuncture at patient service centre
Turnaround
2–4 business days
Collection notes
Phlebotomy at the processing laboratory's draw site (LabCorp, Quest, or Access Medical Laboratories, depending on routing). In premenopausal women, sample ideally drawn in the early follicular phase (cycle days 3–5) to avoid ovulatory peaks; document cycle day or menopausal status on the requisition. Note the performing laboratory and assay method (immunoassay or LC-MS/MS) for serial comparability and to interpret borderline results.
Specimen requirements
Minimum 0.5 mL serum (gel separator acceptable). Separate from cells within two hours; androstenedione is stable refrigerated for several days and frozen for months. Specify assay method if LC-MS/MS is required for paediatric or low-concentration samples.
What can affect A4 results?
Ovarian androstenedione secretion peaks mid-cycle at ovulation, so timing the sample to the early follicular phase (days 3–5) standardises the result in premenopausal women; a random sample may be misleadingly elevated or normal.
Hyperinsulinaemia stimulates ovarian theca-cell androgen synthesis and reduces sex hormone-binding globulin, raising free-androgen concentrations; adipose aromatase also converts androstenedione to oestrone peripherally.
Testosterone, DHEA, and androstenedione supplements all enter the interconversion pool, so a full supplement history is essential before interpreting an elevated result.
Combined oral contraceptives suppress LH-driven ovarian androgen synthesis, and anti-androgens (spironolactone, cyproterone) block androgen receptors or reduce production; baseline testing should ideally precede such therapy.
Immunoassays may cross-react with other steroids and overestimate low concentrations; LC-MS/MS offers greater specificity and is preferred when precision is critical, particularly in children and when results are borderline.
ACTH-driven adrenal androgen secretion rises with stress and cortisol excess, so androstenedione may be modestly elevated in Cushing syndrome or during acute illness.
What do A4 results mean?
Elevated
Ovarian androgen excess (polycystic ovary syndrome, hyperthecosis, androgen-secreting ovarian tumour), adrenal androgen excess (non-classic congenital adrenal hyperplasia due to 21-hydroxylase or 3β-HSD deficiency, Cushing syndrome, adrenal adenoma or carcinoma), premature adrenarche in children, or exogenous androgen or DHEA supplementation. Markedly elevated values (greater than twice the upper limit) warrant imaging and further biochemical evaluation to exclude a tumour. Mild to moderate elevations in the setting of oligo-ovulation and clinical hyperandrogenism are consistent with PCOS.
Normal
A normal androstenedione does not exclude hyperandrogenism — testosterone and free-androgen index may be elevated while androstenedione remains within the reference interval, particularly when SHBG is low. Interpret alongside total and free testosterone, DHEA-S, and 17-hydroxyprogesterone rather than relying on a single marker.
Reduced
Low androstenedione is not commonly clinically significant but may be seen with adrenal insufficiency, gonadal failure, or suppression by exogenous glucocorticoids or oestrogen therapy. In isolation a low value is rarely pursued unless adrenal or gonadal function is otherwise in question.
Note: Androstenedione must be interpreted in the context of sex, age, menstrual phase, and assay method. Because it is a precursor rather than the principal active androgen, modest elevations are common in PCOS and overlap with the upper end of normal in healthy women. The ratio of androstenedione to DHEA-S can help distinguish ovarian-predominant from adrenal-predominant sources, though overlap is substantial. Serial measurements and dynamic testing (ACTH stimulation, dexamethasone suppression) are often required to localise pathology definitively.
Frequently asked questions
Androstenedione is an androgen precursor made by the adrenal glands and gonads that converts to testosterone and oestrone. It is tested to investigate excess androgen production in women with hirsutism or virilisation, to diagnose congenital adrenal hyperplasia, and to evaluate suspected androgen-secreting tumours.
How to access the A4 test
The A4 reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: October 7, 2026
Last reviewed: October 7, 2026
- Carmina E, Lobo RA. Evaluation of hormonal status in women with hyperandrogenism. In: Azziz R, et al., eds. Androgen Excess Disorders in Women. Contemporary Endocrinology. (2006)
- Speiser PW, et al. Congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. (2018)
- Teede HJ, et al. Recommendations from the 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Fertil Steril. (2023)
- Auchus RJ. Steroid 17-monooxygenase and 17,20-lyase activities and human androgen biosynthesis. Trends Endocrinol Metab. (1998)
- Rosenfield RL, Ehrmann DA. The pathogenesis of polycystic ovary syndrome (PCOS): the hypothesis of PCOS as functional ovarian hyperandrogenism revisited. Endocr Rev. (2016)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.
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