Also known as:Luteinizing Hormone; Lutropin; Interstitial Cell Stimulating Hormone; ICSH
Formal name:Luteinizing Hormone, serum or urine
Related tests:FSH,Testosterone, Progesterone, Estrogens, Androstenedione, Semen Analysis, Anti-Mullerian Hormone, Prolactin, SHBG
Why Get Tested?
To evaluate fertility issues, function of reproductive organs (ovaries or testicles), or to detect the release of an egg from the ovary (ovulation); to evaluate pituitary function
In children, to evaluate early or delayed sexual maturation (puberty)
When to Get Tested?
For women, when you are having difficulty getting pregnant or are having irregular or heavy menstrual periods; when you are tracking ovulation during your menstrual cycle
For men, when your partner cannot get pregnant or you have a low sperm count, low muscle mass or decreased sex drive
When your healthcare provider thinks that you have symptoms of a pituitary disorder or hypothalamic disorder
When a health practitioner suspects that a child has delayed or earlier than expected sexual maturation
A blood sample drawn from a vein in your arm; sometimes a random urine sample or a 24-hour urine collection may be taken
Test Preparation Needed?
None, but the timing of a woman's sample will be correlated with her menstrual cycle.
How is it used?
The test for luteinizing hormone (LH), a hormone associated with reproduction and the stimulation of the release of an egg from the ovary (ovulation) in women and testosterone production in men, has several uses.
- In the workup of infertility
- To aid in the diagnosis of pituitary disorders that can affect LH production
- To help diagnose conditions associated with dysfunction of the ovaries or testicles
In women, LH levels are useful:
- In the investigation of menstrual irregularities
- To evaluate LH levels during the menstrual cycle; multiple urine LH tests may be ordered for this purpose. These LH "spot tests" can be performed at home and used to detect the surge in LH that indicates that ovulation will occur in the next 1-2 days. The tests can help determine when a woman is likely to be the most fertile.
In children, FSH and LH are used to diagnose delayed and precocious (early) puberty. Irregular timing of puberty may be an indication of a more serious problem involving the hypothalamus, the pituitary gland, the ovaries or testicles, or other systems. The measurement of LH and FSH may differentiate between benign symptoms and true disease. Once it is established that symptoms are a result of true disease, further testing can be done to discern the underlying cause.
In persons with evidence of poor ovarian or testicular function, LH is sometimes measured in response to administration of gonadotropin releasing hormone (GnRH) to distinguish between disorders involving the hypothalamus or pituitary gland. GnRH is the hormone produced by the hypothalamus that stimulates the pituitary to release LH and FSH. For this test, a baseline blood sample is drawn and then the person is given an injection of GnRH. Subsequent blood samples are drawn at specified times and the level of LH is measured. This test can help differentiate between a disorder of the pituitary (secondary), when LH will not respond to GnRH, or hypothalamus (tertiary), when LH responds to GnRH. It is also often helpful in the evaluation of precocious or delayed puberty.
When is it ordered?
In adults, LH (and FSH) tests may be ordered when:
- A woman is having difficulty getting pregnant or has irregular or an absence of menstrual periods
- When it is suspected that a women has entered menopause and her menstrual cycle has stopped or become irregular
- When a man's partner cannot get pregnant, when he has a low testosterone level, or when he has low muscle mass or decreased sex drive, for example.
- When a health practitioner suspects that a pituitary disorder is present; a pituitary disorder can affect the production of several different hormones so there may be signs and symptoms in addition to infertility that can include fatigue, weakness, unexplained weight loss, and decreased appetite to name a few.
In children, LH and FSH may be ordered when a boy or girl does not appear to be entering puberty at an appropriate age (either too late or too soon). Signs of puberty may include:
- Breast enlargement in girls
- Growth of pubic hair
- Growth of testicles and penis in boys
- Beginning of menstruation in girls
What does the test result mean?
LH and FSH levels can help to differentiate between primary ovarian failure (failure of the ovaries themselves or lack of ovarian development) and secondary ovarian failure (failure of the ovaries due to disorders of either the pituitary or the hypothalamus).
Increased levels of LH and FSH are seen in primary ovarian failure. Some causes of primary ovarian failure are listed below.
- Failure to develop ovaries (ovarian agenesis)
- Chromosomal abnormality, such as Turner syndrome
- Defect in steroid production by the ovaries, such as 17 alpha hydroxylase deficiency
Premature ovarian failure due to:
- Exposure to radiation
- Autoimmune disease
Chronic failure to ovulate (anovulation) due to:
- Polycystic ovary syndrome (PCOS)
- Adrenal disease
- Thyroid disease
- Ovarian tumor
In women who are trying to become pregnant, multiple LH tests can be used to detect the surge that precedes ovulation. An LH surge indicates that ovulation has occurred.
During menopause, a woman's ovaries cease to function; thus LH levels will rise.
Low levels of LH and FSH are seen in secondary ovarian failure and indicate a problem with the pituitary or hypothalamus. See the article on Pituitary Disorders for more information.
High LH levels may indicate primary testicular failure. This can be due to developmental defects in testicular growth or to testicular injury, as described below.
- Failure to develop gonads (gonadal agenesis)
- Chromosomal abnormality, such as Klinefelter syndrome
- Viral infection (mumps)
- Exposure to radiation
- Autoimmune disease
- Germ cell tumor
Low levels of LH and FSH are seen in secondary failure of the testicles and indicate a problem with the pituitary or hypothalamus. See the article on Pituitary Disorders for more information.
In Both Men and Women
LH response to GnRH can help differentiate between secondary dysfunction (failure of the pituitary) and tertiary disorder (a problem involving the hypothalamus). Once the baseline level of LH has been measured, a dose of GnRH is given by injection. A subsequent increase in the level of LH indicates that the pituitary responded to the GnRH and points to a disorder involving the hypothalamus. A reduced level of LH shows that the pituitary did not respond to the GnRH and suggests a disease involving the pituitary.
In young children, high levels of LH and FSH with the development of secondary sexual characteristics at an unusually young age are an indication of precocious puberty. This is much more common in girls than in boys. This premature development is usually due to a problem with the central nervous system and can have a few different underlying causes. Examples include:
- Central nervous system tumor
- Brain injury, trauma
- Inflammation within the central nervous system (e.g., meningitis, encephalitis)
- Brain surgery
Normal prepubescent levels of LH and FSH in children exhibiting some signs of pubertal changes may indicate a condition call "precocious pseudopuberty." The signs and symptoms are brought on by elevated levels of the hormones estrogen or testosterone. This may be caused by:
- Hormone-secreting tumors
- Adrenal gland tumors
- Ovarian tumors or cysts
- Testicular tumors
Normal FSH and LH levels with a few signs of puberty can also be a benign form of precocious puberty with no underlying or discernable cause or may just be a normal variation of puberty. In delayed puberty, LH and FSH levels can be normal or below what is expected for a youth within this age range. The test for LH response to GnRH in addition to other testing may help to diagnose the reason for the delayed puberty. Some of the causes for delayed puberty can include:
- Failure of the ovaries or testicles
- Hormone deficiency
- Turner syndrome
- Klinefelter syndrome
- Chronic infections
- Eating disorder (anorexia nervosa)
Is there anything else I should know?
Some drugs can cause LH to increase, such as anticonvulsants, clomiphene, and naloxone, while others cause LH to decrease, such as digoxin, oral contraceptives, and hormone treatments.
A recent nuclear medicine scan may interfere with results of the LH test if it is measured by a radioimmunoassay, which is seldom used any more.
LH is sometimes referred to as interstitial cell stimulating hormone (ICSH) in males.
What is being tested?
Luteinizing hormone (LH) is a hormone associated with reproduction and the stimulation of the release of an egg from the ovary (ovulation) in women and testosterone production in men. This test measures the amount of luteinizing hormone in the blood or urine.
LH is produced by the pituitary gland, a grape-sized organ found at the base of the brain. Control of LH production is a complex system involving the hypothalamus in the brain, the pituitary gland, and the hormones produced by the ovaries and testicles.
In premenopausal women, several hormones rise and fall in a specific sequence during each menstrual cycle. During the cycle, LH stimulates ovulation and the production of other hormones, estradiol and progesterone.
Womens' menstrual cycles are divided into follicular and luteal phases, with each phase lasting about 14 days. Near the end of the follicular phase, there is a mid-cycle surge of follicle-stimulating hormone (FSH) and LH. This surge triggers ovulation, causing the rupture of the egg follicle on the ovary and the release of the egg.
During the luteal phase, the site where the egg follicle ruptured becomes a "corpus luteum." LH secretion stimulates the corpus luteum to start producing progesterone. FSH and LH levels decline, while progesterone and estradiol concentrations increase. These hormone levels decrease in turn after several days if the egg is not fertilized. Menstruation starts and when it ends, the cycle begins again.
As a woman ages and menopause approaches, ovarian function wanes and eventually ceases. As this occurs, FSH and LH levels rise.
In men, LH stimulates Leydig cells in the testicles to produce testosterone. LH levels are relatively constant in men after puberty. A high testosterone level provides negative feedback to the pituitary gland and the hypothalamus, thus decreasing the amount of LH secreted.
In infants and children, LH levels rise shortly after birth and then fall to very low levels (by 6 months in boys and 1-2 years in girls). At about 6-8 years, levels again rise before the beginning of puberty and the development of secondary sexual characteristics.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm or a random urine sample is used. A 24-hour collection of urine may be requested if a health practitioner wants to measure LH levels produced over a 24-hour period. LH is released intermittently throughout the day; thus, a random sample may not reflect a true reading. A 24-hour urine can eliminate this variation.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but a woman's sample should be collected at specific times during her menstrual cycle.
- I'm having a hard time getting pregnant. What tests do I need?
Basic tests for infertility often include measuring LH and FSH levels. Your healthcare provider may also ask you to keep track of your body temperature, which rises slightly during ovulation. Other hormonal tests as well as a postcoital (after intercourse) examination may also be done. A hysterosalpingogram (image of fallopian tubes) may be ordered to see whether your fallopian tubes are blocked. Your partner may be asked to give a specimen of semen for analysis.
- Can the LH test be used to tell if I have ovulated?
The LH test is often used to predict ovulation by detecting a woman's monthly pre-ovulation LH surge. It indicates ovulation but cannot, however, be used to confirm that ovulation has occurred.
- Why would a man need a test for FSH and LH; I thought these were female hormones?
Men also produce FSH and LH. These hormone levels are important for the male reproduction process, whereby FSH stimulates the testes to produce sperm. This is analogous to FSH stimulation of the ovaries to produce eggs. In men, LH may be measured if testosterone levels are low.
- Is there a home test for LH?
Yes, there is a home test that uses a urine sample to help predict ovulation. For more information, visit the article on Home Tests and the following FDA web site.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.