What is Testosterone?
💡 Testosterone: male normal 10–35 nmol/L (total); female normal 0.5–2.5 nmol/L. In men: low testosterone + high FSH = non-obstructive azoospermia. In women: elevated total testosterone or free androgen index (FAI) = PCOS androgen excess. DHEAS + testosterone + SHBG together interpret androgen status comprehensively.
Testosterone is the primary androgen hormone, produced by the testes in men (Leydig cells) and in smaller amounts by the ovaries and adrenal glands in women. In fertility medicine, testosterone testing serves two entirely different purposes: in men, it assesses Leydig cell function and is part of the azoospermia/oligozoospermia workup; in women, elevated testosterone suggests PCOS or an androgen-secreting tumour.
🇮🇳 India Context: Testosterone is widely assessed and treated across major Indian fertility centres including Chennai, Mumbai, Bangalore, Delhi, and Hyderabad.
What are the key characteristics of Testosterone?
- Male total testosterone: normal 10–35 nmol/L (300–1000 ng/dL); morning sample essential (testosterone peaks 8–10am)
- Hypogonadism in men: total testosterone <10 nmol/L (primary/secondary); causes: Klinefelter syndrome, hypogonadotrophic hypogonadism, hyperprolactinaemia, obesity, exogenous androgen use
- Exogenous testosterone (anabolic steroids, TRT): suppresses LH/FSH → impairs spermatogenesis → oligozoospermia or azoospermia; recovery may take 6–24+ months after stopping
- Female total testosterone: normal 0.5–2.5 nmol/L (varies by lab); measurement alone insufficient — must interpret with SHBG and free androgen index (FAI)
- Free androgen index (FAI) = (testosterone × 100) / SHBG: better marker of biologically active androgen than total testosterone alone; FAI >5 in women = androgen excess
- PCOS androgen profile: elevated total testosterone, elevated free androgen index, low/normal SHBG — classic biochemical fingerprint in hyperandrogenic PCOS
- Androgen-secreting tumour (rare): very high testosterone (>5 nmol/L in women) with rapid virilisation → requires adrenal/ovarian imaging urgently
- Testosterone and IVF priming (controversial): some protocols use low-dose transdermal testosterone pretreatment in poor ovarian responders before IVF to improve AFC and response — evidence mixed
How does Testosterone work?
Why does Testosterone matter in fertility?
In men, testosterone testing is essential in the azoospermia workup — low testosterone with elevated FSH/LH confirms non-obstructive azoospermia (testicular failure). The most important clinical alert is exogenous testosterone use: men on TRT or anabolic steroids are often azoospermic and do not know it until they try to conceive. Cessation + gonadotropin therapy (hMG/FSH + hCG) can restore spermatogenesis in secondary hypogonadism cases. In women, testosterone is a key component of the PCOS biochemical diagnosis — the FAI rather than total testosterone is the more sensitive androgen marker. Hyperandrogenic women with PCOS may need anti-androgen pretreatment (OCP) before ovulation induction to reduce LH excess and improve follicle quality.
What are related terms to Testosterone?
PCOS (Polycystic Ovary Syndrome)
PCOS is a common hormonal disorder where the ovaries produce too many male hormo…
DHEAS (Dehydroepiandrosterone Sulfate)
DHEAS (dehydroepiandrosterone sulfate) is an androgen produced primarily by the …
SHBG (Sex Hormone-Binding Globulin)
SHBG (sex hormone-binding globulin) is a protein produced by the liver that bind…
Semen Analysis
Semen Analysis is the main test for evaluating male fertility. A semen sample is…
Ovulation
Ovulation is the release of a mature oocyte (egg) from a dominant ovarian follic…
FAQs about Testosterone
What does high testosterone mean for a woman's fertility?
Elevated testosterone in women (total testosterone >2.5 nmol/L or FAI >5) causes: anovulation or oligo-ovulation, irregular/absent periods, hirsutism, acne. The most common cause is PCOS. High testosterone disrupts the LH surge and impairs follicle maturation. Management: identify cause (PCOS, CAH, adrenal tumour — rare); treat with OCP + metformin/weight loss for PCOS; letrozole or FSH for ovulation induction once androgen excess is managed.
What does low testosterone mean for a man's fertility?
Low testosterone in men (<10 nmol/L) impairs spermatogenesis. Classify cause first: primary hypogonadism (high FSH/LH + low T = testicular failure) vs secondary hypogonadism (low/normal FSH/LH + low T = pituitary/hypothalamic problem). Secondary hypogonadism is often treatable with gonadotropin therapy (hMG + hCG), which can induce spermatogenesis. Primary hypogonadism (e.g., Klinefelter 47XXY) may require surgical sperm retrieval (micro-TESE) for ICSI.
Can anabolic steroids or testosterone therapy cause infertility?
Yes — severely and commonly missed. Exogenous testosterone (TRT, anabolic steroids) suppresses LH and FSH via negative feedback, shutting down spermatogenesis. Azoospermia is common in men on TRT. Recovery after stopping: 6–24+ months, and sometimes incomplete. Never start testosterone therapy if fertility is desired. If a man presents with azoospermia and is on TRT, stop immediately — gonadotropin therapy (FSH + hCG) can restore spermatogenesis in secondary hypogonadism cases.
What is the free androgen index (FAI)?
FAI = (total testosterone ÷ SHBG) × 100. It measures biologically active testosterone — total testosterone alone misses androgen excess when SHBG is low. Normal female FAI: <5. Elevated FAI (>5) = androgen excess, even if total testosterone appears borderline normal. Example: total testosterone 2.0 nmol/L with SHBG 20 → FAI = 10 (elevated). The same 2.0 nmol/L with SHBG 80 → FAI = 2.5 (normal). Always calculate FAI alongside total testosterone in PCOS workup.
What testosterone level is used for PCOS diagnosis?
PCOS biochemical hyperandrogenism is diagnosed by: elevated total testosterone (>2.5 nmol/L by lab reference) OR elevated free androgen index (FAI >5) OR elevated free testosterone (calculated). LC-MS/MS measurement is more accurate than immunoassay for female testosterone levels. Testosterone alone is often insufficient — SHBG must be measured to calculate FAI. Mildly elevated testosterone with low SHBG = significant biochemical androgen excess even if total testosterone is only borderline elevated.
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