Androstenedione Blood Test

What Does This Test Measure?

Androstenedione is a precursor hormone produced by both the adrenal glands and the gonads. It sits at a junction in the steroid pathway: it can be converted onward into testosterone, or into estrone and then estradiol. It has only weak androgenic activity itself, and most of its clinical importance comes from what it becomes.

Because it is made in roughly equal measure by the adrenals and the gonads, it does not by itself identify a source. Its value lies in being measured alongside other steroids, where the pattern points to one gland or the other.

In the reproductive years it contributes meaningfully to the total androgen pool in women, which is why it is often raised in conditions of androgen excess even when testosterone is unremarkable.

Why Your Doctor Ordered This Test

The usual context is androgen excess in women: hirsutism, persistent acne, scalp hair thinning, irregular or absent periods, or infertility. It is measured alongside testosterone, DHEA-S and 17-hydroxyprogesterone to establish both the degree of excess and its likely source.

It is also central to the diagnosis and monitoring of congenital adrenal hyperplasia, where it is one of the main markers used to judge whether steroid replacement is adequately suppressing adrenal androgen output. In children it forms part of the assessment of early puberty or ambiguous genitalia.

What High Androstenedione Means

Polycystic ovary syndrome is the commonest cause in women of reproductive age, typically producing a modest rise alongside a raised free testosterone and a low SHBG.

Congenital adrenal hyperplasia is the diagnosis that must not be missed. In its most common form, a 21-hydroxylase deficiency blocks cortisol synthesis and shunts precursors into the androgen pathway, raising both androstenedione and 17-hydroxyprogesterone. The non-classical form presents in adolescence or adulthood and can look almost identical to PCOS, which is why 17-hydroxyprogesterone is measured alongside.

A markedly raised androstenedione, particularly with rapid onset of virilisation (deepening voice, clitoral enlargement, male-pattern balding) raises concern for an androgen-secreting tumour of the ovary or adrenal gland and warrants urgent imaging. Cushing's syndrome and adrenal hyperplasia produce more moderate elevations, as does supplementation, since androstenedione has been sold as a sports supplement.

What Low Androstenedione Means

Low androstenedione is far less often clinically significant. It occurs with adrenal insufficiency, where the whole adrenal cortex is underproducing, and with hypopituitarism, where the adrenal drive is absent. It falls naturally with age in both sexes, and in women after removal of the ovaries.

Corticosteroid treatment suppresses adrenal androgen production and lowers androstenedione, which is exactly the intended effect when treating congenital adrenal hyperplasia. In that context a low value may indicate over-treatment rather than a problem to correct upward, and it is interpreted against the steroid dose.

How to Prepare and What Affects the Result

A morning sample is preferred, since adrenal steroid output follows the cortisol rhythm and is highest shortly after waking. In menstruating women the sample is usually taken in the early follicular phase, on day 2 to 5, to avoid the mid-cycle rise, and the cycle day should be recorded.

Corticosteroids in any form suppress results, and where a diagnosis of congenital adrenal hyperplasia is being sought, testing is normally done before treatment starts. Oral contraceptives lower androgen levels and usually need to be stopped for around three months before assessment of androgen excess. Biotin supplements interfere with several immunoassays, and any androstenedione-containing supplement should be declared.

Common Misinterpretations

The main error is treating a raised androstenedione as confirmation of PCOS without excluding non-classical congenital adrenal hyperplasia. The two overlap closely in presentation, and only 17-hydroxyprogesterone, measured in the early morning follicular phase, reliably separates them.

The second is relying on immunoassay results at low concentrations, where cross-reactivity with other steroids makes them unreliable. Mass spectrometry should be used where the value will drive a decision.

The third is interpreting a single mildly raised result as significant. Androstenedione varies with time of day and cycle phase, and modest elevations are common and often unimportant without corroborating clinical features.

Frequently Asked Questions

How does androstenedione differ from testosterone?

Androstenedione is a precursor with only weak androgenic activity of its own; testosterone is the potent end product. Androstenedione can be converted into testosterone or into estrogens, so it sits at a branch point in the pathway. It is useful because it is often raised in androgen excess even when testosterone appears normal.

Why is 17-hydroxyprogesterone tested alongside it?

To distinguish polycystic ovary syndrome from non-classical congenital adrenal hyperplasia, which can look almost identical. In CAH an enzyme block causes both 17-hydroxyprogesterone and androstenedione to rise together. Measuring 17-hydroxyprogesterone in the early morning follicular phase is the standard way to separate the two, and it changes treatment.

What does a very high androstenedione with rapid symptoms mean?

Markedly raised levels with rapidly progressing virilisation (voice deepening, clitoral enlargement, male-pattern balding) raise concern for an androgen-secreting tumour of the ovary or adrenal gland. This pattern warrants prompt imaging rather than watchful waiting, in contrast to the gradual, milder changes typical of PCOS.

Does the contraceptive pill affect this test?

Yes, substantially. Combined oral contraceptives suppress ovarian androgen production and raise SHBG, lowering measured androgen levels. Assessment of androgen excess normally requires stopping hormonal contraception for around three months first, which needs to be planned with your doctor.

Can a low androstenedione mean I am over-treated?

In congenital adrenal hyperplasia, yes. Steroid replacement is intended to suppress adrenal androgen output, and androstenedione is one of the markers used to judge the dose. A very low value may indicate more steroid than necessary, which carries its own risks, so it is read against the treatment rather than as an isolated abnormality.

Related Markers: Read Together for Full Context

BloodWorker reads lab values together, not in isolation. These related markers provide essential context for interpreting your Androstenedione result: