LH is crucial in maintaining the normal function of the male and female reproductive systems.
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This test can also be purchased as part of our Women’s Hormone panel.
PREPARATION: No fasting or other special preparation is needed for this test. However, there are many factors that can affect the outcome of this test, so please read the following carefully:
Taking birth control pills that contain testosterone, estrogen, or progesterone can affect the results of this test. This test may also be adversely affected by other prescription medicines (including cimetidine, clomiphene, digitalis, and levodopa), as well as some over-the-counter medicines, herbs, and natural substances. So if you might be taking any of these medications or supplements you should ask your treating physician whether and/or when you should stop them prior to performing this test.
The radioactive substances used in nuclear imaging tests can also interfere with LH levels, so you should also speak with your doctor before having this test if you have had a recent thyroid scan, bone scan, or other study that used a radioactive dye.
What does this test do?
This test determines the concentration of luteinizing hormone (LH) circulating in the bloodstream.
Why is this important?
Luteinizing hormone (LH) is produced by a part of the brain called the pituitary gland. It works together with another messenger called Follicle stimulating hormone, and both have extremely important effects on both male and female sexual development as well as reproductive physiology.
In women, LH helps control ovulation and regulate the menstrual cycle. In men, LH plays a key role in testosterone secretion and is necessary for sperm to develop.
Measuring the amount of LH can be useful in evaluating the functions of the sex organs, and is often used to help ascertain potential causes of infertility in both men and women.
This test is also used in evaluating pituitary gland function, and to help diagnose the cause of early (precocious) or delayed puberty in children.
What do the results mean?
The range of LH levels considered to be normal is variable, and depends on several factors including the person’s age and stage of sexual development at the time the testing is performed.
Once men have reached adulthood the amount of LH usually remains constant. A low value is a sign that the pituitary gland is not functioning properly, and can be the cause of a low sperm count. An elevated level of LH can be seen with certain pituitary gland tumors, or result from a loss of testicular function.
In women who haven’t reached menopause the blood level of LH varies significantly throughout the menstrual cycle, so it is important to know the first day of the last menstrual period before the test is performed.
The LH level increases rapidly to reach its highest concentration just before ovulation occurs, which is about midway through the cycle (e.g. day 14 of a 28-day cycle). When used in treating infertility, the LH test can be repeated several times to help pinpoint the exact time of ovulation, which is when the ovary releases an egg.
LH levels that remain persistently high indicate a condition called primary ovarian failure, where the ovaries aren’t functioning properly. Elevated levels of LH can also be the result of certain pituitary gland tumors.
In contrast, persistently low levels of FSH may be a sign of secondary ovarian failure, which suggests a problem with the pituitary gland. This is frequently found as a cause of infertility because this can lead to a decreased egg supply in women.
The LH test is also performed when a boy or girl has not entered puberty as expected, or appears to be entering puberty early. Low levels are found in the delayed onset of puberty, and high levels are linked to early onset (or precocious) puberty.