In men, FSH levels are used to help determine the reason for a low sperm count.
In children, FSH and LH are used to help diagnose delayed or 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.
For a woman, an FSH test may be ordered when she is having difficulty getting pregnant or has irregular or an absence of menstrual periods.
FSH may be ordered when a woman's menstrual cycle has stopped or become irregular, to determine if the woman has entered menopause.
For a man, the test may be ordered when his partner cannot get pregnant, when he has a low sperm count, or when he has low muscle mass or decreased sex drive, for example.
In both women and men, testing may be ordered 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 some of those listed above. They can include fatigue, weakness, unexplained weight loss, and decreased appetite to name a few.
In children, FSH and LH 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:
As part of an infertility workup, a high or low FSH is not diagnostic but provides a piece of information on what may be the cause. For example, a hormone imbalance may affect a woman's menstrual cycle and/or ovulation. A health practitioner will consider all the information from the workup to establish a diagnosis. See the Infertility article for more on this.
FSH and LH levels can help to differentiate between primary ovarian failure (failure of the ovaries themselves) and secondary ovarian failure (failure of the ovaries due to disorders of either the pituitary or the hypothalamus).
High levels of FSH and LH are consistent with primary ovarian failure. Some causes of primary ovarian failure are listed below.
When a woman enters menopause and her ovaries stop working, FSH levels will rise.
Low levels of FSH and LH are consistent with secondary ovarian failure due to a pituitary disorder or hypothalamic problem. Low FSH serum levels have been associated with increased risk of ovarian cancer.
High FSH levels are due to primary testicular failure. This can be the result of developmental defects in testicular growth or to testicular injury, as indicated below.
Low levels are consistent with pituitary or hypothalamic disorders. See the article on Pituitary Disorders for more information.
High levels of FSH and LH 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:
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:
FSH results can be increased with use of certain drugs, including cimetidine, clomiphene, digitalis, and levodopa. FSH results can be decreased with oral contraceptives, phenothiazines, and hormone treatments. FSH will also be low when women are pregnant. A recent nuclear medicine scan may interfere with results of the FSH test if it is measured by a radioimmunoassay, which is seldom used any more.
This article was last reviewed on May 5, 2014. | This article was last modified on February 24, 2015.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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