A luteinizing hormone test measures how much luteinizing hormone a person has in their blood. This is a hormone with key roles in both male and female reproductive systems.
This article explores the uses of LH tests. It discusses high, low, and normal LH levels, as well as what they mean and how they relate to pregnancy.
An LH test is a type of blood test that measures a person's LH levels.
LH is made in the pituitary gland of the brain. LH is a sex hormone that affects how a person's reproductive organs work. In females, LH affects the ovaries. In males, it affects the testes.
Reproductive health problems can affect a person's LH levels.
LH is involved in the following bodily processes:
- Puberty: LH levels affect the onset of puberty. High LH levels may cause early puberty and low LH levels may delay puberty.
- Menstruation: LH works with another sex hormone called follicle-stimulating hormone (FSH) to control menstrual cycles.
- Ovulation: An increase in LH, called an LH surge, triggers the release of an egg from an ovary.
- Progesterone release: An increase in LH triggers ovulation. The cell structure that is left after ovulation releases progesterone. Progesterone is needed to maintain a pregnancy.
- Testosterone production: LH binds to Leydig cells in the testes and triggers testosterone production. Testosterone levels affect sex drive.
- Sperm production: Testosterone, which LH levels affect, is needed for sperm production.
We explore the various uses of LH tests below:
Doctors use LH tests to help diagnose fertility problems in both males and females. If a couple is having difficulty become pregnant, there may be a problem with:
- sperm count
- the egg supply from the ovaries
A person's LH levels can tell the doctor whether a person is having problems with their sperm count or egg supply. Either issue could make it more difficult for a person to become pregnant.
People can measure their LH levels to find out how fertile they are on different days. LH levels surge just before ovulation, signaling the most fertile period of a female's menstrual cycle.
To identify the fertile period, people can check their LH levels at home. They can do this using ovulation urine tests. These home tests can detect the surge in LH that happens 1–1.5 days before ovulation.
Ovulation test kits normally contain several urine tests. The best time to use them is around the middle of the menstrual cycle, which is usually when a female ovulates. This may help her determine when she is about to ovulate.
Having sex around the time of ovulation is a good idea if a couple wants to become pregnant.
When a woman goes through menopause, her LH levels rise. For this reason, LH tests can help a doctor diagnose a person's menstrual changes or problems.
Early or late puberty
LH levels can help a doctor determine why a child or teenager may have started puberty early or late. High LH levels may cause early puberty. Low LH levels may cause late puberty.
Pituitary gland problems
LH is made in the pituitary gland. Measuring LH levels can help determine whether there is a problem with the pituitary gland.
LH tests can help a doctor diagnose low testosterone in a male. Symptoms of low testosterone include:
The normal range of LH varies between males, females, and children. LH test results are measured in international units per liter (IU/L).
The following information is a guide to what high, low, and normal LH levels mean. People should discuss their LH test results with a doctor.
Normal ranges in men
For males, the normal range is 1.24–7.8 IU/L.
If LH levels are below the normal range, it may indicate a pituitary gland problem. Their pituitary gland may not be making enough LH, which may lead to low testosterone.
If LH levels are too high, the testes may not be responding to LH properly. LH may not be triggering testosterone production in the way that it should.
Normal ranges in women
For females, the normal range depends on where they are in their menstrual cycle, as follows:
- follicular phase, or the beginning of the cycle: 1.68–15 IU/L
- mid-cycle peak, around the middle of the cycle: 21.9–56.6 IU/L
- luteal phase, which is the end of the cycle: 0.61–16.3 IU/L
For females who have gone through menopause, the normal range is 14.2–52.3 IU/L.
If LH levels are higher than normal when a person is not ovulating, they may be experiencing menopause. High LH levels may also indicate a pituitary disorder or polycystic ovary syndrome.
If the LH levels are lower than normal, it may indicate:
Normal ranges in children
For girls who are yet to go through puberty (aged around 1–10 years), the normal range is 0.03–3.9 IU/L.
An LH test is a safe procedure, though having any blood test involves a low risk of:
- feeling lightheaded
People who are afraid of needles or prone to fainting should let the doctor know before they get a blood test.
Doctors use a simple blood test to measure a person's LH levels. They will draw a sample of a person's blood using a needle and send it to a laboratory for testing.
People can also measure their LH levels at home using a home ovulation test. This is a urine test that involves adding a few drops of urine to a test strip. Follow the instructions on the package.
To diagnose issues with a woman's ovaries, the doctor may also carry out an FSH test.
Increased levels of both LH and FSH may indicate primary ovarian insufficiency. In this condition, the ovaries stop working properly before the female reaches the age of 40.
LH test results help a doctor determine whether a male or female has problems with their reproductive system. Doctors also use LH tests to diagnose pituitary gland problems and the early or late onset of puberty.
Females can take LH urine tests at home to work out when they are ovulating, which can help them conceive. A person is most fertile around ovulation.