What are FSH and LH?
FSH (follicle-stimulating hormone) and LH (luteinising hormone) are gonadotropins produced by the pituitary gland. In women, FSH stimulates ovarian follicle development and oestrogen production; LH triggers ovulation. In men, FSH stimulates sperm production (spermatogenesis) in the testes; LH stimulates testosterone production from Leydig cells. These hormones are part of the hypothalamic-pituitary-gonadal (HPG) axis and are used to evaluate fertility, menopause and pituitary problems.
FSH and LH normal ranges
| Group | FSH (mIU/mL) | LH (mIU/mL) |
|---|---|---|
| Women — follicular phase (day 2-3) | 3 – 10 | 2 – 15 |
| Women — LH surge (ovulation) | Up to 40+ | Up to 100+ (surge) |
| Women — luteal phase | 1 – 9 | 1 – 13 |
| Post-menopausal women | > 25 (typically 25-135) | > 14 |
| Adult men | 1.5 – 12.4 | 1.7 – 8.6 |
What does HIGH FSH mean in women?
High FSH in women — reduced ovarian reserve
A high FSH on day 2-3 of the menstrual cycle (the basal FSH) is the most important marker of ovarian reserve (the pool of eggs remaining). High FSH means the pituitary is working harder to stimulate the ovaries, which are responding less. FSH above 10 mIU/mL is considered elevated; above 25 indicates premature ovarian insufficiency (POI) or natural menopause. High FSH combined with high LH and low oestrogen in a young woman indicates premature ovarian failure. In menopause, both FSH and LH are persistently elevated.
What does HIGH LH in women mean?
High LH in women — PCOS or LH surge
An elevated LH to FSH ratio greater than 2:1 or 3:1 — especially on day 2-3 of the cycle — is a classic pattern of polycystic ovary syndrome (PCOS). It reflects increased pituitary stimulation from insulin resistance and elevated androgens. Isolated high LH at mid-cycle (around day 14) is the normal ovulation surge and is the basis of LH ovulation predictor kits.
What do LOW FSH and LH mean?
Low FSH and LH — hypothalamic or pituitary failure
Low levels in both men and women indicate the signal from the brain is insufficient — called secondary or hypogonadotrophic hypogonadism. Causes: pituitary tumour (prolactinoma, other adenoma), excessive exercise or eating disorders (hypothalamic amenorrhoea), high prolactin, anabolic steroid use (suppresses natural production), and significant stress or illness. In men, low LH means less testosterone is being made (secondary hypogonadism).
What do HIGH FSH and LH mean in men?
High FSH and LH in men — primary testicular failure
High gonadotropins in men mean the pituitary is trying to stimulate the testes, but the testes are not responding (primary hypogonadism). Causes: Klinefelter syndrome (XXY), bilateral undescended testes, chemotherapy or radiation damage, mumps orchitis, testicular torsion injury.
Questions to ask your doctor
- Should I test on day 2 or day 3 of my cycle?
- Do I need an AMH (anti-Mullerian hormone) test to check my egg reserve?
- What is my FSH:LH ratio?
- Does this result mean I am in menopause?
- Should I see a fertility specialist or endocrinologist?