FSH and LH (Gonadotrophins) Test
The FSH and LH test measures both pituitary gonadotrophins together to assess the hypothalamic-pituitary-gonadal axis. Their relative pattern localises dysfunction: both are elevated in primary gonadal failure and both are low or inappropriately normal in central causes.
2
Biomarkers
Blood (serum)
Sample
1–3 business days
Turnaround
No
Fasting
What is the FSH & LH test?
The FSH and LH Test measures both pituitary gonadotrophins together, providing a combined assessment of the hypothalamic-pituitary-gonadal axis. Measuring the two in tandem is standard practice because their relative pattern, more than either value alone, localises the level at which reproductive or gonadal dysfunction arises. In the diagnostic landscape, paired FSH and LH are a first-line investigation in menstrual disturbance, suspected menopause or primary ovarian insufficiency, infertility, and hypogonadism in both sexes. The key interpretive value lies in the pattern: both gonadotrophins are elevated in primary gonadal failure, where reduced feedback drives them up, and both are low or inappropriately normal in central (secondary) causes despite low gonadal hormones. The LH-to-FSH ratio adds specific information in polycystic ovary syndrome. As with any gonadotrophin measurement in women, results are meaningful only in relation to the menstrual cycle phase or menopausal status, and the panel is interpreted alongside the relevant gonadal steroids.
What does the FSH & LH test measure?
Follicle-stimulating hormone is a pituitary glycoprotein gonadotrophin secreted under pulsatile GnRH control, with feedback from gonadal steroids and inhibin. In women it drives ovarian follicular recruitment and varies sharply across the menstrual cycle; in men it supports Sertoli cell function and spermatogenesis.
FSH assesses the hypothalamic-pituitary-gonadal axis. A raised FSH indicates reduced gonadal feedback (menopause, primary ovarian insufficiency, primary testicular failure), while a low or inappropriately normal FSH with low gonadal hormones points to a central cause. It is interpreted with LH and the gonadal steroids.
Luteinising hormone is a pituitary glycoprotein gonadotrophin sharing a common alpha subunit with FSH and secreted under pulsatile GnRH control. In women a mid-cycle LH surge triggers ovulation and supports corpus luteum function; in men it stimulates testicular Leydig cells to produce testosterone.
LH complements FSH in assessing the gonadal axis and localising dysfunction. The LH surge underlies ovulation, and the LH-to-FSH ratio is relevant in polycystic ovary syndrome, where LH is often disproportionately elevated. In men, LH distinguishes primary testicular failure (high LH) from secondary hypogonadism (low or inappropriately normal LH).
Why is the FSH & LH test ordered?
- Evaluation of suspected menopause or perimenopause in women with menstrual change and vasomotor symptoms
- Investigation of suspected primary ovarian insufficiency in women under 40 with oligomenorrhoea or amenorrhoea
- Female infertility and ovulatory assessment, interpreting the gonadotrophin pattern with cycle timing and supporting markers
- Assessment of amenorrhoea or oligomenorrhoea to distinguish ovarian, pituitary, and hypothalamic causes
- Support for the assessment of polycystic ovary syndrome, where the LH-to-FSH ratio is informative
- Male hypogonadism workup to distinguish primary testicular failure (high gonadotrophins) from secondary causes (low or inappropriately normal)
- Evaluation of delayed or precocious puberty as part of gonadotrophin assessment
- Investigation of suspected pituitary dysfunction where gonadotrophin output is being characterised
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Venipuncture at patient service centre
Turnaround
1–3 business days
Collection notes
In women, record the menstrual cycle day; baseline and ovarian reserve assessment use early-follicular (day 2–5) sampling, and the cycle phase must accompany the request. Document hormonal contraceptives, hormone therapy, GnRH analogues, and high-dose biotin. FSH and LH are interpreted together and with the relevant sex steroids.
Specimen requirements
Minimum 0.5 mL serum. Separate serum from cells within 2 hours of collection.
What can affect FSH & LH results?
Both gonadotrophins change markedly across the cycle, with a mid-cycle LH surge, so in women results are interpretable only with the cycle day. Ovarian reserve and baseline assessment use early-follicular (day 2–5) sampling.
Exogenous oestrogen and progestogen suppress gonadotrophin secretion through feedback, lowering both FSH and LH and obscuring the underlying axis. A washout interval may be required.
These agents alter pituitary gonadotrophin release — initial stimulation then suppression with agonists, direct suppression with antagonists — substantially changing both hormones depending on agent and timing.
Both gonadotrophins, and LH especially, are released in pulses, so a single measurement may not capture the average; borderline results may warrant repeat sampling.
High-dose biotin can interfere with streptavidin-biotin immunoassay platforms, producing falsely altered FSH and LH depending on assay design.
Endogenous antibodies can interfere with immunoassay measurement, producing spurious results discordant with the clinical picture. # REVIEWER FLAG: Confirm assay susceptibility and mitigation with Quest.
What do FSH & LH results mean?
Elevated
Both gonadotrophins elevated indicates reduced gonadal feedback — menopause or primary ovarian insufficiency in women, primary testicular failure in men. A disproportionately raised LH relative to FSH supports a polycystic ovary syndrome pattern in the appropriate context. A raised early-follicular FSH suggests diminished ovarian reserve.
Normal
Normal gonadotrophins, interpreted with cycle phase and gonadal steroids, are consistent with an intact axis. In women, values must be read against the menstrual day, and normal results do not exclude subtle ovarian reserve decline when other markers are abnormal.
Reduced
Low or inappropriately normal FSH and LH with low gonadal hormones indicate a secondary (hypothalamic or pituitary) cause, such as hypogonadotrophic hypogonadism or pituitary insufficiency. Suppression by exogenous sex steroids should be excluded first.
Note: FSH and LH must be interpreted together, with the menstrual cycle phase in women, and alongside the relevant gonadal steroids; the pattern is more informative than either value alone. Pulsatile secretion means a single value can mislead, and exogenous hormones suppress both. The LH-to-FSH ratio is a supportive, not standalone, feature in polycystic ovary syndrome. Reference ranges differ sharply by sex, age, and cycle phase.
Frequently asked questions
Their relative pattern localises dysfunction more reliably than either alone. Both are elevated in primary gonadal failure and both are low or inappropriately normal in central causes, and together they yield the LH-to-FSH ratio used in PCOS.
How to access the FSH & LH test
The FSH & LH 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: June 3, 2026
Last reviewed: June 3, 2026
- Practice Committee of the American Society for Reproductive Medicine. Testing and interpreting measures of ovarian reserve. Fertil Steril. (2020)
- Webber L, et al. ESHRE Guideline: management of women with premature ovarian insufficiency. Hum Reprod. (2016)
- Teede HJ, et al. International evidence-based guideline for the assessment and management of polycystic ovary syndrome. Hum Reprod. (2018)
- Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. (2018)
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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