Luteinizing hormone (LH) is an important hormone both men
and women produce. This hormone is known as a gonadotropin, and it affects the
sex organs in both men and women. For women, it affects ovaries, and in men, it
affects the testes. LH plays a role in puberty, menstruation, and fertility.
Knowing the amount of LH in your blood can indicate
underlying problems associated with a variety of reproductive health issues.
What Is Luteinizing Hormone?
LH is a hormone that’s produced in the pituitary gland. The
pituitary gland is located at the base of the brain, and it’s roughly the size
of a pea. If you’re a woman, LH is an important part of your menstrual cycle.
It works with follicle-stimulating hormone (FSH), which another gonadotropin
made in the pituitary gland. FSH stimulates the ovarian follicle, causing an
egg to grow. It also triggers the production of estrogen in the follicle.
The rise in estrogen tells your pituitary gland to stop
producing FSH and to start making more LH. The shift to LH causes the egg to be
released from the ovary, a process called ovulation. In the empty follicle,
cells proliferate, turning it into a corpus luteum. This structure releases
progesterone, a hormone necessary to maintain pregnancy. If pregnancy doesn’t occur,
the levels of progesterone drop off and the cycle begins again.
If you’re a man, your pituitary gland also produces LH. The
hormone binds to receptors in certain cells in your testes called Leydig cells.
This leads to the release of testosterone, a hormone that’s necessary for
producing sperm cells.
What Is a Luteinizing Hormone Blood Test?
An LH blood test measures the amount of LH in your
bloodstream. If you’re a woman, the amount of this hormone in your bloodstream
varies throughout the menstrual cycle and changes with pregnancy. If a doctor
orders a test for LH related to fertility, a woman may need multiple tests to
track the rising and falling hormone levels. LH levels can also be measured by
analyzing a urine sample.
If you’re a man, your doctor can order an LH test to
establish a baseline LH level. Your doctor can also measure your LH level after
giving you an injection of gonadotropin releasing hormone (GnRH). Measuring LH
after receiving this hormone can tell your doctor if you have a problem with
the pituitary gland or with another part of your body.
What Are the Reasons for Requesting a Luteinizing Hormone Blood Test?
There are many reasons for your doctor to request an LH
blood test. Levels of LH relate to menstrual issues, fertility, and the onset
Examples of instances when your doctor may order an LH blood
- A woman is having difficulty getting pregnant
- A woman has irregular or absent menstrual
- It’s suspected that a woman has entered
- A man has signs of low testosterone levels, such
as low muscle mass or decrease in sex drive.
- A pituitary disorder is suspected.
- A boy or girl appears to be entering puberty too
late or too soon.
Your doctor may order the LH blood test in coordination with
other hormone measurements, such as testosterone, progesterone, FSH, and
Menstrual Cycle and Menopause
If you have absent or irregular periods, your doctor may
want to determine the amount of LH in your bloodstream to find an underlying
cause. LH levels should rise after menopause because your ovaries no longer
function and take cues from LH.
Your doctor may order an LH blood test if you’re having
difficulty conceiving. LH levels can indicate the supply of eggs in a woman’s
ovaries and a man’s sperm count, both of which affect fertility.
For a younger patient, a doctor may order an LH blood test
to find the underlying causes for delayed or early puberty. A doctor will
consider if a person is or isn’t showing signs of puberty. These include breast
growth and menstruation in girls, testicle and penis growth in boys, and pubic
hair growth in both boys and girls.
A test of LH levels in the urine can be used to determine
when you’re ovulating. When LH levels start to increase, this can indicate
ovulation will likely occur within one to two days. These types of tests can be
done at home and are often used to enhance the chances of conceiving. It’s
important to note that this is accomplished with a urine test and not a blood
How Is the Test Administered?
To administer an LH blood test, a health professional will
draw a small amount of blood from you, most likely from your arm. The short
procedure will be done in your doctor’s office or at a lab. The sample will
then be analyzed for LH levels.
To draw blood, a health professional will wrap your upper
arm with an elastic band to make your veins easier to see. They will disinfect
the skin and insert a needle into a vein on the inside of your arm. A tube
attached to the needle will collect a small sample of your blood. The process
is short and mostly painless.
Your doctor may request that you have samples of blood drawn
each day for several days. Because the amount of LH in the blood varies with
your menstrual cycle, a few samples may be necessary to get an accurate
measurement of your LH levels.
What Are the Risks Associated With a Luteinizing Hormone Blood Test?
There aren’t many risks associated with having blood drawn.
The needle site may bruise afterwards, but if you put pressure on it with a
bandage, you can reduce this possibility.
Phlebitis, while rare, may occur when blood is drawn. This
is when the vein becomes inflamed after blood is taken. If it occurs, your
healthcare provider will likely have you apply a warm compress to the vein
throughout the day. If you have any kind of bleeding disorder, make sure to
tell your doctor to avoid complications from having blood drawn.
How Should I Prepare for a Luteinizing Hormone Blood Test?
Your doctor should give you exact directions to prepare for
your blood test. You may be told to stop taking certain medications that can
affect the results, so be sure to inform your doctor of all medications and
supplements you take. You may need to stop taking birth control or other
hormone pills for up to four weeks before the test. Your doctor will also want
to know the date of your last period.
As with many blood draws, you may be asked to avoid eating
or drinking for up to eight hours leading up to the test.
If you’ve had any type of test or procedure with a
radioactive substance seven days before the LH blood test, let your doctor know.
These substances can interfere with the results of your test.
Understanding the Results of an LH Test
Your doctor can tell you when results of your test will be
available and will discuss the meaning of your levels with you. According to
of Pathology and Laboratory Medicine at the University of California, San
Francisco, the following values are normal LH blood levels measured in
international units per liter (IU/L):
- women in the follicular phase of the menstrual
cycle: 1.9 to 12.5 IU/L
- women at the peak of the menstrual cycle: 8.7 to
- women in the luteal phase of the menstrual
cycle: 0.5 to 16.9 IU/L
- pregnant women: less than 1.5 IU/L
- women past menopause: 15.9 to 54.0 IU/L
- women using contraceptives: 0.7 to 5.6 IU/L
- men between the ages of 20 and 70: 0.7 to 7.9
- men over 70: 3.1 to 34 IU/L
While each result can vary based on your unique condition,
some general interpretations of LH results can include the following.
If you’re a woman, increased levels of LH and FSH can
indicate a problem with your ovaries. This is known as primary ovarian failure.
Some causes of primary ovarian failure can include:
- ovaries that are not properly developed
- genetic abnormalities, such as Turner syndrome
- exposure to radiation
- history of taking chemotherapy drugs
- autoimmune disorders
- ovarian tumor
- thyroid or adrenal disease
- polycystic ovary syndrome (PCOS)
Low levels of both LH and FSH can indicate secondary ovarian
failure. This means another part of your body causes ovarian failure. In many
cases, this is the result of problems with the areas of your brain that make hormones,
such as the pituitary gland.
If you’re a man, high LH levels can indicate primary
testicular failure. The causes of this condition can include:
- chromosome abnormalities, such as Klinefelter
- gonad development failure
- a history of viral infections, such as the mumps
- radiation exposure
- history of taking chemotherapy medications
- autoimmune disorders
- tumors, such as a germ cell tumor
Secondary testicular failure can also be due to a
brain-related cause, such as a disorder in the hypothalamus. Also, if your
doctor has given you the GnRH shot and your LH levels went down or stayed the
same, a pituitary disease is often to blame.
For children, high levels of LH can cause early puberty.
This is known as precocious puberty. According to the American
Association of Clinical Chemistry (AACC), girls are more likely to
experience this condition than boys. Underlying causes of this can include:
- a tumor in the central nervous system
- trauma or brain injury
- inflammation or infection in the central nervous
system, such as meningitis or encephalitis
- a history of brain surgery
Delayed puberty with normal or lower LH levels can indicate
underlying disorders, including:
- ovarian or testicular failure
- hormone deficiency
- Turner syndrome
- Klinefelter syndrome
- chronic infection
- an eating disorder
Medications that can change LH levels include:
- hormone treatments
- birth control pills
Testing LH has the potential to indicate a number of
development- and fertility-related disorders. If your doctor suspects you may
have a condition that affects the ovaries, testicles, or the parts of the brain
that make LH, the test can provide more information.