Testosterone in Women: Low and High Results and Their Causes

A woman's testosterone comes from several sources: it is secreted by the ovaries (theca cells and stroma) and the adrenal glands, and a considerable part is formed peripherally from androstenedione and DHEA. In the blood most testosterone is bound to proteins - mainly sex hormone-binding globulin (SHBG) and albumin - and only a small fraction circulates free, the most biologically active form. Two women with identical total testosterone can therefore have different amounts of free testosterone if their SHBG differs. We write about how SHBG changes interpretation in the entries on SHBG and on total and free testosterone in the knowledge base.

Measurement is hard because concentrations in women are very low and popular immunoassays were designed mainly with male levels in mind. The Endocrine Society position statement on testosterone measurement stresses that laboratories should be assessed on their ability to measure samples of known concentration accurately and precisely, and that normal values for both sexes and children should be set only after the methods are standardised. A review devoted to mass spectrometry notes that LC-MS/MS is particularly suited to detecting the low testosterone concentrations typical of women and children.

What does this mean for the patient? A woman's testosterone result should be read together with information on the method used. If the result is unexpected, does not fit the symptoms, or the patient uses contraception or has SHBG disorders (for example in pregnancy or hypothyroidism), it is worth asking the laboratory about the method and, if possible, repeating the measurement by LC-MS/MS at a reference laboratory. Concretely: a woman with a 'high' testosterone on an older-generation assay and high SHBG may in reality have a normal result, and one with a 'normal' result and low SHBG may have a raised one.

For comparability, in menstruating women blood is usually drawn in the morning in the early follicular phase (cycle days 2-5), although testosterone varies less across the cycle than oestradiol or progesterone. With absent periods the test can be done at any time, but the result is interpreted in the context of other hormones. Tell your doctor about hormonal contraception (it lowers free testosterone and raises SHBG), supplements (for example DHEA; biotin can interfere with some immunoassays) and drugs.

Raised testosterone in a woman of reproductive age most often results from polycystic ovary syndrome (PCOS), in which the ovaries produce an excess of androgens and cycles are irregular. Typical features are irregular or infrequent periods, acne, excess hair growth (hirsutism), male-pattern hair loss, a tendency to weight gain and insulin resistance. Diagnosing PCOS requires meeting defined criteria and excluding other causes; we describe the condition in the PCOS entry of the knowledge base. A high result alone is not enough to make the diagnosis.

An important alarm signal is rapid progression of symptoms: within a few months marked hirsutism, deepening of the voice, male-pattern hair loss, clitoral enlargement or cessation of periods. In that situation do not wait for further cycles - urgent endocrine work-up with imaging is needed. The testosterone concentration itself is then often much higher than in typical PCOS; the thresholds above which a tumour is looked for differ between sources, so the decision rests with the doctor.

Remember too that total testosterone can be normal while signs of androgen excess are present if SHBG is low and free testosterone is raised. That is why in women with hirsutism and normal total testosterone, free testosterone or the FAI is assessed. In addition, the severity of hirsutism depends on the sensitivity of hair follicles to androgens, not only on the blood concentration.

The answer may be surprising: in women there is no recognised diagnosis of 'testosterone deficiency' based on a blood result. International guidelines on using testosterone for hypoactive sexual desire disorder (HSDD) stress that total testosterone should not be used to diagnose HSDD - it serves only as a baseline for monitoring therapy. This is because testosterone levels correlate poorly with desire, and the normal range is wide and depends on the assay.

A low result can be caused by: hormonal contraception (it suppresses ovarian androgen production and raises SHBG), age (testosterone gradually declines from early adulthood), removal of the ovaries or premature ovarian insufficiency, adrenal insufficiency, hypopituitarism, chronic glucocorticoids, malnutrition and low BMI. Natural menopause itself does not cause a sharp fall in total testosterone, because the ovaries continue to produce some androgens after menopause, but the level falls after bilateral oophorectomy. Possible symptoms - lower desire, fatigue, low mood - are non-specific and have many other causes that must be considered first.

The best available evidence is a meta-analysis of randomised, double-blind trials: the review included 36 trials (46 publications) with 8480 participants, lasting at least 12 weeks. In postmenopausal women, testosterone, compared with placebo or another treatment, significantly improved sexual function: frequency of satisfying sexual events (mean difference 0.85), desire (standardised mean difference 0.36), pleasure, arousal, orgasm and responsiveness, and reduced sexual concerns and distress. No effect was shown on body composition, musculoskeletal health or cognitive function, although data on these were scarce.

On this basis, the guideline of the International Society for the Study of Women's Sexual Health (ISSWSH, 2021) recommends systemic transdermal testosterone in women with HSDD not primarily related to modifiable factors (for example relationship problems or mental health). According to the guideline, available research supports a moderate therapeutic benefit, and safety data showed no serious adverse events at physiological doses, but long-term safety has not been established. The guideline warns against compounded preparations because of a lack of data on efficacy and safety, requires the patient's informed consent and monitoring of concentrations so as to keep them in the physiological premenopausal range, and calls for checks for signs of androgen excess.

Combined hormonal contraception, especially oral, increases the liver's production of SHBG, which reduces the amount of free testosterone - which is why it is used in treating acne and hirsutism. At the same time it suppresses ovarian androgen production. A woman's total testosterone result on contraception may therefore look 'normal' or low, even though it was raised before she started. This is why PCOS and hyperandrogenism work-up is best done off contraception, if possible - the decision on any break is made with the doctor.

SHBG also changes for many other reasons. It is lowered by insulin resistance, obesity, hypothyroidism, androgen excess and high doses of glucocorticoids. It is raised by oral oestrogens, hyperthyroidism, pregnancy and restrictive eating. Free androgen indices calculated from total testosterone and SHBG can therefore differ from each other and from a direct measurement of free testosterone - which in turn depends on the method, as described above. You will find more about SHBG in the SHBG entries of the knowledge base.

What this text does not cover: it is not instructions for using testosterone, does not discuss treatment of PCOS or hirsutism, does not concern hormone therapy in transgender people and does not replace a consultation. The Islam et al. meta-analysis and the ISSWSH guideline concern mainly postmenopausal women with HSDD; results need not carry over to other populations. The testosterone ranges given are approximate and should always be looked up on your own report, because they depend on the method and the laboratory.

Testosterone in women is a test that is easy to order and hard to interpret well. We recommend three rules: first, know the method and units; second, do not look to this one result for the answer to every symptom - libido, energy and mood have many other, more common causes; third, do not reach for testosterone or 'androgen' supplements without a specialist's advice. If the problem is androgen excess - acne, hirsutism, irregular cycles - effective work-up and treatment of PCOS or another cause is available and worth pursuing.