The test for follicle-stimulating hormone (FSH), a hormone associated with reproduction and the development of eggs in women and sperm in men, has several uses.

In both women and men, the test may be used with other hormone tests such as luteinizing hormone (LH), testosterone, estradiol, and/or progesterone to help:

• Determine the cause of infertility
• Diagnose conditions associated with dysfunction of the ovaries or testicles
• Aid in the diagnosis of pituitary or hypothalamus disorders, which can affect FSH production

In women, FSH levels are also useful in:

• The investigation of menstrual irregularities
• Predicting onset or confirmation of menopause

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:

• Breast enlargement in girls
• Growth of pubic hair
• Growth of the testicles and penis in boys
• Beginning of menstruation in girls

Results of an FSH test are typically considered with results of other hormone tests, such as LH , estrogens, and/or testosterone.

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.

In Women

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.

Developmental defects:

• Failure to develop ovaries (ovarian agenesis)
• Chromosomal abnormality, such as Turner syndrome
• Defect in the steroid production by the ovaries, such as 17 alpha hydroxylase deficiency

Premature failure of the ovaries due to:

• Radiation exposure
• Chemotherapy
• Autoimmune disease

Chronic failure to ovulate (anovulation) due to:

• Polycystic ovary syndrome (PCOS)
• Adrenal disease
• Thyroid disease
• Ovarian tumor

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.

In Men

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.

Developmental defects:

• Failure to develop gonads (gonadal agenesis)
• Chromosomal abnormality, such as Klinefelter syndrome

Testicular failure:

• Viral infection (mumps)
• Trauma
• Radiation exposure
• Chemotherapy
• Autoimmune disease
• Germ cell tumor

Low levels are consistent with pituitary or hypothalamic disorders. See the article on Pituitary Disorders for more information.

In Children

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:

• 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. Some of the causes for delayed puberty can include:

• Dysfunction of the ovaries or testicles
• Hormone deficiency
• Turner syndrome
• Klinefeltersyndrome
• Chronic infections
• Cancer
• Eating disorder (anorexia nervosa)

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.