LH (Luteinizing Hormone)

What is LH

LH (luteinizing hormone) is a gonadotropic hormone produced by the pituitary gland (the brain's anterior gland). LH plays an important role in the reproductive system in both men and women.

In women, LH regulates the menstrual cycle and ovulation — in the middle of the cycle, LH rises sharply (called the LH surge), triggering the release of an egg. In men, LH stimulates Leydig cells in the testes to produce testosterone.

LH is often tested alongside FSH (follicle-stimulating hormone), as both hormones work together and their ratio provides additional diagnostic information.

Reference ranges

Men: 1.7–8.6 IU/L (international units per litre).

Women — LH varies considerably depending on the phase of the menstrual cycle:

• Follicular phase: ~2–15 IU/L
• Ovulation surge: ~20–90 IU/L
• Luteal phase: ~1–17 IU/L
• Menopause: ~15–60 IU/L

The specific reference ranges are always provided by the laboratory according to cycle phase. The laboratory reference range is the most important one to use.

Why LH may be elevated

• Menopause and perimenopause — a natural rise in LH in women as the ovaries become less responsive to pituitary signals.
• Primary gonadal insufficiency — when the ovaries or testes are underperforming, the pituitary increases LH production (a compensatory mechanism).
• Polycystic ovary syndrome (PCOS) — an elevated LH/FSH ratio is frequently observed.
• Pituitary adenoma — a rare case where a pituitary tumour produces excess LH.
• Mid-cycle surge — a physiologically normal rise at the time of ovulation.

Why LH may be low

• Hypothalamic or pituitary disorders — a central cause where the brain fails to send adequate signals.
• Stress- or exercise-induced amenorrhoea — intense sport, very low body weight, or chronic stress can suppress LH secretion.
• Hormonal contraception — contraceptive pills, patches, or implants suppress LH and FSH production.
• Hyperprolactinaemia — elevated prolactin can suppress LH release.
• Anabolic steroid use — can significantly reduce LH in men.

Next steps

An LH result must be interpreted in context: in women, in relation to the day of the cycle; in men, alongside testosterone levels. A single measurement rarely provides a complete picture.

If LH is significantly abnormal, a doctor may recommend:

• Additional testing of FSH, oestradiol, testosterone, or prolactin.
• For women — repeating the test on a specific day of the cycle.
• Imaging of the ovaries or pituitary gland.

Monitoring over time

LH trends matter more than a single value. For women planning pregnancy, monitoring LH helps identify the timing of ovulation. During perimenopause, LH trends indicate the stage of transition.

In men, persistently low LH combined with low testosterone may indicate central hypogonadism — important information for a doctor.

Questions for your doctor

1. Does my LH level correspond to my cycle phase (women) or age-appropriate range? 2. What is my LH-to-FSH ratio and what does it indicate? 3. Do I need additional hormonal tests? 4. Could my medications or contraception be affecting my LH result? 5. How often should I repeat this test?

*This is not medical advice. Please consult your doctor regarding any health decisions.*