Measures luteinizing hormone (LH) to help assess fertility.
What is being tested?
Luteinizing hormone (LH) is a hormone associated with reproduction. Its stimulation of either ovary or testicles results in the release of an egg from the ovary (ovulation) in women or testosterone production in men. This test measures the amount of luteinizing hormone in the blood.
LH is produced by the pituitary gland, a small organ located in the center of the head behind the sinus cavity 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 women of childbearing age, several hormones (LH, follicle-stimulating hormone (FSH), estrogen and progesterone) rise and fall in a specific sequence during each menstrual cycle. 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 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 release 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 released.
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 test used?
In both women and men, the LH test is often used in conjunction with other tests (FSH, testosterone, estradiol and progesterone) to help diagnose:
- The cause of infertility
- Pituitary disorders that can affect LH production
- Conditions that affect the function of the ovaries or testicles
In women, LH levels are useful for:
- Investigating irregular periods (menstrual cycles)
- Evaluating 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.
GNRH stimulation test:
In people with signs and symptoms of poor ovarian or testicular function, a gonadotropin releasing hormone (GnRH) stimulation test may be performed. GnRH is the hormone produced by the hypothalamus that stimulates the pituitary to release LH and FSH. This test allows for assessment of the pituitary gland’s ability to make LH in response to GnRH administration. 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 the serum LH level will not increase in response to GnRH, or hypothalamus (tertiary), when LH will increase in response to GnRH injection.
In children, FSH and LH tests are used in the diagnosis of 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 can help in differentiating between benign symptoms and true disease. The GnRH stimulation test can assess pituitary function in pubertal disorders: the increase of serum LH to a certain level in response to administration of GnRH would suggest a pituitary gland that is primed for pubertal hormone responses. Further testing can then be done to discern the underlying cause.
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 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 care 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.
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?
Results of an LH test are typically considered with results of other hormone tests, such as FSH, estrogens, and/or testosterone.
LH and FSH levels can help to differentiate between conditions affecting the ovaries themselves (primary) and dysfunction of the ovaries due to disorders of either the pituitary or the hypothalamus (secondary).
Increased levels of LH and FSH are seen in the following:
- Failure to develop ovaries (ovarian agenesis)
- Chromosome disorder, such as Turner syndrome
- Defect in steroid production by the ovaries, such as 17 alpha hydroxylase deficiency
Damage or injury to the ovaries due to:
- Exposure to radiation
- Autoimmune disease
Underlying conditions that affect ovary function, such as:
- Polycystic ovary syndrome (PCOS)
- Adrenal disease
- Thyroid disease
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 may be seen in problems with the pituitary or hypothalamus.
High LH levels may indicate a condition affecting the testicles themselves. Some examples include:
- Viral infection (mumps)
- Trauma, injury
- Exposure to radiation
- Autoimmune disease
- Germ cell tumor
- Failure to develop normal gonads (gonadal agenesis or gonadal dysgenesis)
- Chromosome disorder, such as Klinefelter syndrome
Low levels of LH and FSH may indicate a problem with the pituitary or hypothalamus.
In Both Men and Women
LH response to GnRH can help differentiate between a pituitary disorder and 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, higher levels of LH and FSH than expected for age when paired with the development of secondary sexual characteristics at an unusually young age are an indication of early 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)
Normal prepubescent levels of LH and FSH in children exhibiting signs of puberty (e.g., development of pubic hair and acne) may indicate a condition brought on by elevated levels of the hormones estrogen or testosterone. This may be caused by:
- Exposure to estrogen or testosterone creams or gels
- Premature adrenarche (an early awakening of the adrenal glands)
- Tumors that produce hormones
- Adrenal gland tumors
- Ovarian tumors or cysts
- Testicular tumors
Normal FSH and LH levels with a few signs of puberty may be a normal variation of puberty.
In delayed puberty, LH and FSH levels can be high, 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)
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. FSH stimulates the testicles to produce sperm. 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, see this FDA website.
Is there anything else I should know?
Some drugs can cause LH to increase, such as anticonvulsants, clomiphene, naloxone, and ketoconazole, while others cause LH to decrease, such as digoxin, oral contraceptives, and hormone treatments.