What it measures
LH (luteinising hormone) is made by the pituitary gland at the base of the brain. In men it signals the testes to make testosterone, and in women a surge of LH sets off ovulation. The test measures how much is in the blood.
Why people test it
- Read with testosterone in men, to see whether low testosterone starts in the testes or the pituitary.
- Measured with FSH in fertility tests and when looking into irregular or missed periods.
- Used with FSH when looking into the menopause or polycystic ovary syndrome.
- TRT and anabolic steroids switch off the body's own LH, so it reads low while they are in use.
- Checked after a steroid cycle to see whether the body's own testosterone production has restarted.
Typical range
Ranges vary between labs, with the method used, age and sex, and your report shows the lab's own range. For men, one NHS trust lab gives 0.6 to 12.1 IU/L. For women the range depends on the stage of the menstrual cycle, peaks sharply mid-cycle and is higher after the menopause. Source: Oxford University Hospitals NHS Foundation Trust: biochemistry reference ranges.
Finger-prick or vein?
A vein draw is usually advised. LH is often tested alongside testosterone or oestradiol, and gels or creams on the fingers can contaminate a finger-prick sample's hormone results.
In women who have periods, LH changes through the cycle, so the day of the cycle the sample is taken affects the result.