LH (luteinising hormone)

Women: 2.4 to 12.6 IU/L · Men: 1.7 to 8.6 IU/L

In women the range depends on cycle phase (about 2.4 to 12.6 IU/L in the first half, a brief mid-cycle peak of 14 to 96, then 1 to 11 in the second half) and is higher after the menopause (roughly 8 to 59).

LH is a messenger hormone from the pituitary gland. In women a sharp mid-cycle surge of LH triggers the release of an egg; in men it tells the testes to make testosterone. It is almost always measured with FSH, and the two are read together.

It is requested for irregular or absent periods, polycystic ovary syndrome, fertility assessment, early menopause, and in men with low testosterone. Home ovulation kits detect the same LH surge in urine.

• The mid-cycle surge that triggers ovulation, briefly
• The menopause and the years leading up to it
• Polycystic ovary syndrome, where LH is often higher relative to FSH
• Ovaries or testes that are working less well, from any cause
• Older age in men, in the general population

• The combined contraceptive pill, HRT and other hormone medicines
• Pregnancy
• Low body weight, heavy exercise, stress and eating disorders
• Pituitary or hypothalamus problems, which are uncommon
• Anabolic steroid and testosterone use in men
• High prolactin

• A sample taken near mid-cycle catches the natural surge
• Hormonal contraception suppresses it
• It is released in pulses, so two samples an hour apart can differ

In women it is usually taken between day 2 and day 5 of the cycle with FSH, and the day should be noted. It is released in pulses, so a single value is a snapshot.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.